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    The Principles of Psychology
    The Principles of Psychology
    The Principles of Psychology
    Ebook1,529 pages16 hours

    The Principles of Psychology

    By William James

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    • Consciousness

    • Psychology

    • Apperception

    • Inner Struggle

    • Hidden Knowledge

    • Mind Control

    • Memory Loss

    • Search for Self

    • Power of Thought

    • Hypnosis

    • Battle of Ideas

    • Mystery of Consciousness

    About this ebook

    Experience the life-changing power of William James with this unforgettable book.
    LanguageEnglish
    PublisherScarlet Tree Press
    Release dateDec 16, 2020
    ISBN9791220251730
    The Principles of Psychology
    Author

    William James

    William James (1842–1910) was an American philosopher, physician, and psychologist. The brother of novelist Henry James, William James is remembered for his contributions to the fields of pragmatism and functional psychology. 

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      Book preview

      The Principles of Psychology - William James

      Principles of Psychology, Volume 1

      by William James

                                        TO

                                  MY DEAR FRIEND

                                FRANÇOIS PILLON.

                            AS A TOKEN OF AFFECTION,

                        AND AN ACKNOWLEDGMENT OF WHAT I OWE

                                      TO THE

                              CRITIQUE PHILOSOPHIQUE.

      PREFACE.

      The treatise which follows has in the main grown up in connection with

      the author's class-room instruction in Psychology, although it is true

      that some of the chapters are more 'metaphysical,' and others fuller of

      detail, than is suitable for students who are going over the subject

      for the first time. The consequence of this is that, in spite of the

      exclusion of the important subjects of pleasure and pain, and moral and

      æsthetic feelings and judgments, the work has grown to a length which

      no one can regret more than the writer himself. The man must indeed be

      sanguine who, in this crowded age, can hope to have many readers for

      fourteen hundred continuous pages from his pen. But _wer Vieles bringt

      wird Manchem etwas bringen_; and, by judiciously skipping according to

      their several needs, I am sure that many sorts of readers, even those

      who are just beginning the study of the subject, will find my book of

      use. Since the beginners are most in need of guidance, I suggest for

      their behoof that they omit altogether on a first reading chapters 6,

      7, 8, 10 (from page 330 to page 371), 12, 13, 15, 17, 20, 21, and 28.

      The better to awaken the neophyte's interest, it is possible that the

      wise order would be to pass directly from chapter 4 to chapters 23, 24,

      25, and 26, and thence to return to the first volume again. Chapter

      20, on Space-perception, is a terrible thing, which, unless written

      with all that detail, could not be fairly treated at all. An abridgment

      of it, called 'The Spatial Quale,' which appeared in the Journal of

      Speculative Philosophy, vol. xiii, p. 64, may be found by some persons

      a useful substitute for the entire chapter.

      I have kept close to the point of view of natural science throughout

      the book. Every natural science assumes certain data uncritically, and

      declines to challenge the elements between which its own 'laws' obtain,

      and from which its own deductions are carried on. Psychology, the

      science of finite individual minds, assumes as its data (1) _thoughts

      and feelings_, and (2) _a physical world_ in time and space with which

      they coexist and which (3) _they know_. Of course these data themselves

      are discussable; but the discussion of them (as of other elements) is

      called metaphysics and falls outside the province of this book. This

      book, assuming that thoughts and feelings exist and are vehicles of

      knowledge, thereupon contends that psychology when she has ascertained

      the empirical correlation of the various sorts of thought or feeling

      with definite conditions of the brain, can go no farther--can go

      no farther, that is, as a natural science. If she goes farther she

      becomes metaphysical. All attempts to _explain_ our phenomenally given

      thoughts as products of deeper-lying entities (whether the latter be

      named 'Soul,' 'Transcendental Ego,' 'Ideas,' or 'Elementary Units

      of Consciousness') are metaphysical. This book consequently rejects

      both the associationist and the spiritualist theories; and in this

      strictly positivistic point of view consists the only feature of it

      for which I feel tempted to claim originality. Of course this point of

      view is anything but ultimate. Men must keep thinking; and the data

      assumed by psychology, just like those assumed by physics and the other

      natural sciences, must some time be overhauled. The effort to overhaul

      them clearly and thoroughly is metaphysics; but metaphysics can only

      perform her task well when distinctly conscious of its great extent.

      Metaphysics fragmentary, irresponsible, and half-awake, and unconscious

      that she is metaphysical, spoils two good things when she injects

      herself into a natural science. And it seems to me that the theories

      both of a spiritual agent and of associated 'ideas' are, as they figure

      in the psychology-books, just such metaphysics as this. Even if their

      results be true, it would be as well to keep them, _as thus presented_,

      out of psychology as it is to keep the results of idealism out of

      physics.

      I have therefore treated our passing thoughts as integers, and

      regarded the mere laws of their coexistence with brain-states as the

      ultimate laws for our science. The reader will in vain seek for any

      closed system in the book. It is mainly a mass of descriptive details,

      running out into queries which only a metaphysics alive to the weight

      of her task can hope successfully to deal with. That will perhaps be

      centuries hence; and meanwhile the best mark of health that a science

      can show is this unfinished-seeming front.

      The completion of the book has been so slow that several chapters

      have been published successively in Mind, the Journal of Speculative

      Philosophy, the Popular Science Monthly, and Scribner's Magazine.

      Acknowledgment is made in the proper places.

      The bibliography, I regret to say, is quite unsystematic. I have

      habitually given my authority for special experimental facts; but

      beyond that I have aimed mainly to cite books that would probably

      be actually used by the ordinary American college-student in his

      collateral reading. The bibliography in W. Volkmann von Volkmar's

      Lehrbuch der Psychologie (1875) is so complete, up to its date,

      that there is no need of an inferior duplicate. And for more recent

      references, Sully's Outlines, Dewey's Psychology, and Baldwin's

      Handbook of Psychology may be advantageously used.

      Finally, where one owes to so many, it seems absurd to single out

      particular creditors; yet I cannot resist the temptation at the end of

      my first literary venture to record my gratitude for the inspiration I

      have got from the writings of J. S. Mill, Lotze, Renouvier, Hodgson,

      and Wundt, and from the intellectual companionship (to name only five

      names) of Chauncey Wright and Charles Peirce in old times, and more

      recently of Stanley Hall, James Putnam, and Josiah Royce.

      HARVARD UNIVERSITY, August 1890.

      CONTENTS.

      CHAPTER I.

      THE SCOPE OF PSYCHOLOGY,

      Mental Manifestations depend on Cerebral Conditions, 1. Pursuit of ends

      and choice are the marks of Mind's presence.

      CHAPTER II.

      THE FUNCTIONS OF THE BRAIN

      Reflex, semi-reflex, and voluntary acts. The Frog's nerve-centres.

      General notion of the hemispheres. Their Education--the Meynert

      scheme. The phrenological contrasted with the physiological

      conception. The localization of function in the hemispheres.

      The motor zone. Motor Aphasia. The sight-centre. Mental

      blindness. The hearing-centre. Sensory Aphasia. Centres

      for smell and taste. The touch-centre. Man's Consciousness

      limited to the hemispheres. The restitution of function. Final

      correction of the Meynert scheme. Conclusions.

      CHAPTER III.

      ON SOME GENERAL CONDITIONS OF BRAIN-ACTIVITY

      The summation of Stimuli. Reaction-time. Cerebral blood-supply,

      97. Cerebral Thermometry. Phosphorus and Thought.

      CHAPTER IV.

      HABIT

      Due to plasticity of neural matter. Produces ease of action.

      Diminishes attention, 115. Concatenated performances. Ethical

      implications and pedagogic maxims.

      CHAPTER V.

      THE AUTOMATON-THEORY

      The theory described. Reasons for it. Reasons against it.

      CHAPTER VI.

      THE MIND-STUFF THEORY

      Evolutionary Psychology demands a Mind-dust. Some alleged proofs

      that it exists. Refutation of these proofs. Self-compounding

      of mental facts is inadmissible. Can states of mind be

      unconscious? Refutation of alleged proofs of unconscious thought.

      Difficulty of stating the connection between mind and brain.

      'The Soul' is logically the least objectionable hypothesis.

      Conclusion.

      CHAPTER VII.

      THE METHODS AND SNARES OF PSYCHOLOGY

      Psychology is a natural Science. Introspection, 185. Experiment.

      Sources of error. The 'Psychologist's fallacy'.

      CHAPTER VIII.

      THE RELATIONS OF MINDS TO OTHER THINGS

      Time relations: lapses of Consciousness--Locke _v_. Descartes. The

      'unconsciousness' of hysterics not genuine. Minds may split into

      dissociated parts. Space-relations: the Seat of the Soul.

      Cognitive relations. The Psychologist's point of view. Two

      kinds of knowledge, acquaintance and knowledge about.

      CHAPTER IX.

      THE STREAM OF THOUGHT, 224

      Consciousness tends to the personal form. It is in constant

      change. It is sensibly continuous. 'Substantive' and

      'transitive' parts of Consciousness. Feelings of relation.

      Feelings of tendency. The 'fringe' of the object. The feeling

      of rational sequence. Thought possible in any kind of mental

      material. Thought and language. Consciousness is cognitive.

      The word Object. Every cognition is due to one integral pulse

      of thought. Diagrams of Thought's stream. Thought is always

      selective.

      CHAPTER X.

      THE CONSCIOUSNESS OF SELF

      The Empirical Self or Me. Its constituents. The material

      self. The Social Self. The Spiritual Self. Difficulty of

      apprehending Thought as a purely spiritual activity. Emotions of

      Self. Rivalry and conflict of one's different selves. Their

      hierarchy. What Self we love in 'Self-love'. The Pure Ego.

      The verifiable ground of the sense of personal identity. The

      passing Thought is the only Thinker which Psychology requires.

      Theories of Self-consciousness: 1) The theory of the Soul. 2) The

      Associationist theory. 3) The Transcendentalist theory. The

      mutations of the Self. Insane delusions. Alternating selves.

      Mediumships or possessions. Summary.

      CHAPTER XI.

      ATTENTION

      Its neglect by English psychologists. Description of it.

      To how many things can we attend at once? Wundt's experiments

      on displacement of date of impressions simultaneously attended to.

      Personal equation. The varieties of attention. Passive

      attention. Voluntary attention. Attention's effects on

      sensation;--on discrimination;--on recollection;--on

      reaction-time. The neural process in attention: 1) Accommodation

      of sense-organ. 2) Preperception. Is voluntary attention a

      resultant or a force? The effort to attend can be conceived as a

      resultant. Conclusion. Acquired Inattention.

      CHAPTER XII.

      CONCEPTION

      The sense of sameness. Conception defined. Conceptions are

      unchangeable. Abstract ideas, 468. Universals. The conception

      'of the same' is not the 'same state' of mind.

      CHAPTER XIII.

      DISCRIMINATION AND COMPARISON

      Locke on discrimination. Martineau _ditto_. Simultaneous

      sensations originally fuse into one object. The principle of

      mediate comparison. Not all differences are differences of

      composition. The conditions of discrimination. The sensation

      of difference. The transcendentalist theory of the perception

      of differences uncalled for. The process of analysis. The

      process of abstraction. The improvement of discrimination by

      practice. Its two causes. Practical interests limit our

      discrimination. Reaction-time after discrimination. The

      perception of likeness, 528. The magnitude of differences. The

      measurement of discriminative sensibility: Weber's law. Fechner's

      interpretation of this as the psycho-physic law. Criticism

      thereof.

      CHAPTER XIV.

      ASSOCIATION

      The problem of the connection of our thoughts. It depends on

      mechanical conditions. Association is of objects thought of,

      not of 'ideas'. The rapidity of association. The 'law of

      contiguity'. The elementary law of association. Impartial

      redintegration. Ordinary or mixed association. The law of

      interest. Association by similarity. Elementary expression of

      the difference between the three kinds of association. Association

      in voluntary thought. Similarity no elementary law. History

      of the doctrine of association.

      CHAPTER XV.

      THE PERCEPTION OF TIME, 605

      The sensible present. Its duration is the primitive

      time-perception. Accuracy of our estimate of short durations.

      We have no sense for empty time. Variations of our time-estimate.

      The feeling of past time is a present feeling. Its cerebral

      process.

      CHAPTER XVI.

      MEMORY

      Primary memory. Analysis of the phenomenon of memory.

      Retention and reproduction are both caused by paths of association

      in the brain. The conditions of goodness in memory. Native

      retentiveness is unchangeable. All improvement of memory consists

      in better _thinking_. Other conditions of good memory.

      Recognition, or the sense of familiarity. Exact measurements of

      memory. Forgetting. Pathological cases. Professor Ladd

      criticised.

      INDEX.

      PSYCHOLOGY.

      CHAPTER I.

      THE SCOPE OF PSYCHOLOGY.

      Psychology is the Science of Mental Life, both of its phenomena

      and of their conditions. The phenomena are such things as we call

      feelings, desires, cognitions, reasonings, decisions, and the like;

      and, superficially considered, their variety and complexity is such as

      to leave a chaotic impression on the observer. The most natural and

      consequently the earliest way of unifying the material was, first,

      to classify it as well as might be, and, secondly, to affiliate the

      diverse mental modes thus found, upon a simple entity, the personal

      Soul, of which they are taken to be so many facultative manifestations.

      Now, for instance, the Soul manifests its faculty of Memory, now of

      Reasoning, now of Volition, or again its Imagination or its Appetite.

      This is the orthodox 'spiritualistic' theory of scholasticism and of

      common-sense. Another and a less obvious way of unifying the chaos is

      to seek common elements in the divers mental facts rather than a common

      agent behind them, and to explain them constructively by the various

      forms of arrangement of these elements, as one explains houses by

      stones and bricks. The 'associationist' schools of Herbart in Germany,

      and of Hume the Mills and Bain in Britain have thus constructed a

      _psychology without a soul_ by taking discrete 'ideas,' faint or

      vivid, and showing how, by their cohesions, repulsions, and forms

      of succession, such things as reminiscences, perceptions, emotions,

      volitions, passions, theories, and all the other furnishings of an

      individual's mind may be engendered. The very Self or _ego_ of the

      individual comes in this way to be viewed no longer as the pre-existing

      source of the representations, but rather as their last and most

      complicated fruit.

      Now, if we strive rigorously to simplify the phenomena in either of

      these ways, we soon become aware of inadequacies in our method. Any

      particular cognition, for example, or recollection, is accounted for

      on the soul-theory by being referred to the spiritual faculties of

      Cognition or of Memory. These faculties themselves are thought of as

      absolute properties of the soul; that is, to take the case of memory,

      no reason is given why we should remember a fact as it happened, except

      that so to remember it constitutes the essence of our Recollective

      Power. We may, as spiritualists, try to explain our memory's failures

      and blunders by secondary causes. But its _successes_ can invoke no

      factors save the existence of certain objective things to be remembered

      on the one hand, and of our faculty of memory on the other. When,

      for instance, I recall my graduation-day, and drag all its incidents

      and emotions up from death's dateless night, no mechanical cause can

      explain this process, nor can any analysis reduce it to lower terms or

      make its nature seem other than an ultimate _datum_, which, whether we

      rebel or not at its mysteriousness, must simply be taken for granted if

      we are to psychologize at all. However the associationist may represent

      the present ideas as thronging and arranging themselves, still, the

      spiritualist insists, he has in the end to admit that _something_,

      be it brain, be it 'ideas,' be it 'association,' _knows_ past time

      _as_ past, and fills it out with this or that event. And when the

      spiritualist calls memory an 'irreducible faculty,' he says no more

      than this admission of the associationist already grants.

      And yet the admission is far from being a satisfactory simplification

      of the concrete facts. For why should this absolute god-given Faculty

      retain so much better the events of yesterday than those of last

      year, and, best of all, those of an hour ago? Why, again, in old

      age should its grasp of childhood's events seem firmest? Why should

      illness and exhaustion enfeeble it? Why should repeating an experience

      strengthen our recollection of it? Why should drugs, fevers, asphyxia,

      and excitement resuscitate things long since forgotten? If we content

      ourselves with merely affirming that the faculty of memory is so

      peculiarly constituted by nature as to exhibit just these oddities,

      we seem little the better for having invoked it, for our explanation

      becomes as complicated as that of the crude facts with which we

      started. Moreover there is something grotesque and irrational in the

      supposition that the soul is equipped with elementary powers of such an

      ingeniously intricate sort. Why _should_ our memory cling more easily

      to the near than the remote? Why should it lose its grasp of proper

      sooner than of abstract names? Such peculiarities seem quite fantastic;

      and might, for aught we can see _a priori_, be the precise opposites of

      what they are. Evidently, then, _the faculty does not exist absolutely,

      but works under conditions_; and _the quest of the conditions_ becomes

      the psychologist's most interesting task.

      However firmly he may hold to the soul and her remembering faculty, he

      must acknowledge that she never exerts the latter without a _cue_, and

      that something must always precede and _remind_ us of whatever we are

      to recollect. An _idea_, says the associationist, "an idea associated

      with the remembered thing; and this explains also why things repeatedly

      met with are more easily recollected, for their associates on the

      various occasions furnish so many distinct avenues of recall." But this

      does not explain the effects of fever, exhaustion, hypnotism, old age,

      and the like. And in general, the pure associationist's account of our

      mental life is almost as bewildering as that of the pure spiritualist.

      This multitude of ideas, existing absolutely, yet clinging together,

      and weaving an endless carpet of themselves, like dominoes in ceaseless

      change, or the bits of glass in a kaleidoscope,--whence do they get

      their fantastic laws of clinging, and why do they cling in just the

      shapes they do?

      For this the associationist must introduce the order of experience in

      the outer world. The dance of the ideas is a copy, somewhat mutilated

      and altered, of the order of phenomena. But the slightest reflection

      shows that phenomena have absolutely no power to influence our ideas

      until they have first impressed our senses and our brain. The bare

      existence of a past fact is no ground for our remembering it. Unless

      we have seen it, or somehow _undergone_ it, we shall never know of its

      having been. The expediences of the body are thus one of the conditions

      of the faculty of memory being what it is. And a very small amount

      of reflection on facts shows that one part of the body, namely, the

      brain, is the part whose experiences are directly concerned. If the

      nervous communication be cut off between the brain and other parts,

      the experiences of those other parts are non-existent for the mind.

      The eye is blind, the ear deaf, the hand insensible and motionless.

      And conversely, if the brain be injured, consciousness is abolished or

      altered, even although every other organ in the body be ready to play

      its normal part. A blow on the head, a sudden subtraction of blood, the

      pressure of an apoplectic hemorrhage, may have the first effect; whilst

      a very few ounces of alcohol or grains of opium or hasheesh, or a whiff

      of chloroform or nitrous oxide gas, are sure to have the second. The

      delirium of fever, the altered self of insanity, are all due to foreign

      matters circulating through the brain, or to pathological changes in

      that organ's substance. The fact that the brain is the one immediate

      bodily condition of the mental operations is indeed so universally

      admitted nowadays that I need spend no more time in illustrating it,

      but will simply postulate it and pass on. The whole remainder of the

      book will be more or less of a proof that the postulate was correct.

      Bodily experiences, therefore, and more particularly brain-experiences,

      must take a place amongst those conditions of the mental life of which

      Psychology need take account. _The spiritualist and the associationist

      must both be 'cerebralists'_, to the extent at least of admitting that

      certain peculiarities in the way of working of their own favorite

      principles are explicable only by the fact that the brain laws are a

      codeterminant of the result. Our first conclusion, then, is that a

      certain amount of brain-physiology must be presupposed or included in

      Psychology.[1]

            *      *      *      *      *

      In still another way the psychologist is forced to be something of a

      nerve-physiologist. Mental phenomena are not only conditioned _a parte

      ante_ by bodily processes; but they lead to them _a parte post_. That

      they lead to _acts_ is of course the most familiar of truths, but I do

      not merely mean acts in the sense of voluntary and deliberate muscular

      performances. Mental states occasion also changes in the calibre of

      blood-vessels, or alteration in the heart-beats, or processes more

      subtle still, in glands and viscera. If these are taken into account,

      as well as acts which follow at some _remote period_ because the mental

      state was once there, it will be safe to lay down the general law

      that _no mental modification ever occurs which is not accompanied or

      followed by a bodily change_. The ideas and feelings, _e.g_., which

      these present printed characters excite in the reader's mind not only

      occasion movements of his eyes and nascent movements of articulation in

      him, but will some day make him speak, or take sides in a discussion,

      or give advice, or choose a book to read, differently from what would

      have been the case had they never impressed his retina. Our psychology

      must therefore take account not only of the conditions antecedent to

      mental states, but of their resultant consequences as well.

            *      *      *      *      *

      But actions originally prompted by conscious intelligence may grow

      so automatic by dint of habit as to be apparently unconsciously

      performed. Standing, walking, buttoning and unbuttoning, piano-playing,

      talking, even saying one's prayers, may be done when the mind is

      absorbed in other things. The performances of animal _instinct_ seem

      semi-automatic, and the _reflex acts_ of self-preservation certainly

      are so. Yet they resemble intelligent acts in bringing about the

      _same ends_ at which the animals' consciousness, on other occasions,

      deliberately aims. Shall the study of such machine-like yet purposive

      acts as these be included in Psychology?

      The boundary-line of the mental is certainly vague. It is better not

      to be pedantic, but to let the science be as vague as its subject,

      and include such phenomena as these if by so doing we can throw any

      light on the main business in hand. It will ere long be seen, I trust,

      that we can; and that we gain much more by a broad than by a narrow

      conception of our subject. At a certain stage in the development

      of every science a degree of vagueness is what best consists with

      fertility. On the whole, few recent formulas have done more real

      service of a rough sort in psychology than the Spencerian one that

      the essence of mental life and of bodily life are one, namely, 'the

      adjustment of inner to outer relations.' Such a formula is vagueness

      incarnate; but because it takes into account the fact that minds

      inhabit environments which act on them and on which they in turn

      react; because, in short, it takes mind in the midst of all its

      concrete relations, it is immensely more fertile than the old-fashioned

      'rational psychology,' which treated the soul as a detached existent,

      sufficient unto itself, and assumed to consider only its nature and

      properties. I shall therefore feel free to make any sallies into

      zoology or into pure nerve-physiology which may seem instructive

      for our purposes, but otherwise shall leave those sciences to the

      physiologists.

            *      *      *      *      *

      Can we state more distinctly still the manner in which the mental life

      seems to intervene between impressions made from without upon the body,

      and reactions of the body upon the outer world again? Let us look at a

      few facts.

      If some iron filings be sprinkled on a table and a magnet brought near

      them, they will fly through the air for a certain distance and stick

      to its surface. A savage seeing the phenomenon explains it as the

      result of an attraction or love between the magnet and the filings.

      But let a card cover the poles of the magnet, and the filings will

      press forever against its surface without its ever occurring to them

      to pass around its sides and thus come into more direct contact with

      the object of their love. Blow bubbles through a tube into the bottom

      of a pail of water, they will rise to the surface and mingle with the

      air. Their action may again be poetically interpreted as due to a

      longing to recombine with the mother-atmosphere above the surface. But

      if you invert a jar full of water over the pail, they will rise and

      remain lodged beneath its bottom, shut in from the outer air, although

      a slight deflection from their course at the outset, or a re-descent

      towards the rim of the jar when they found their upward course impeded,

      would easily have set them free.

      If now we pass from such actions as these to those of living things,

      we notice a striking difference. Romeo wants Juliet as the filings

      want the magnet; and if no obstacles intervene he moves towards her by

      as straight a line as they. But Romeo and Juliet, if a wall be built

      between them, do not remain idiotically pressing their faces against

      its opposite sides like the magnet and the filings with the card. Romeo

      soon finds a circuitous way, by scaling the wall or otherwise, of

      touching Juliet's lips directly. With the filings the path is fixed;

      whether it reaches the end depends on accidents. With the lover it is

      the end which is fixed, the path may be modified indefinitely.

      Suppose a living frog in the position in which we placed our bubbles

      of air, namely, at the bottom of a jar of water. The want of breath

      will soon make him also long to rejoin the mother-atmosphere, and he

      will take the shortest path to his end by swimming straight upwards.

      But if a jar full of water be inverted over him, he will not, like the

      bubbles, perpetually press his nose against its unyielding roof, but

      will restlessly explore the neighborhood until by re-descending again

      he has discovered a path round its brim to the goal of his desires.

      Again the fixed end, the varying means!

      Such contrasts between living and inanimate performances end by leading

      men to deny that in the physical world final purposes exist at all.

      Loves and desires are to-day no longer imputed to particles of iron or

      of air. No one supposes now that the end of any activity which they

      may display is an ideal purpose presiding over the activity from its

      outset and soliciting or drawing it into being by a sort of _vis a

      fronte_. The end, on the contrary, is deemed a mere passive result,

      pushed into being _a tergo_, having had, so to speak, no voice in its

      own production. Alter the pre-existing conditions, and with inorganic

      materials you bring forth each time a different apparent end. But

      with intelligent agents, altering the conditions changes the activity

      displayed, but not the end reached; for here the idea of the yet

      unrealized end co-operates with the conditions to determine what the

      activities shall be.

            *      *      *      *      *

      _The pursuance of future ends and the choice of means for their

      attainment are thus the mark and criterion of the presence of

      mentality_ in a phenomenon. We all use this test to discriminate

      between an intelligent and a mechanical performance. We impute no

      mentality to sticks and stones, because they never seem to move for

      _the sake of_ anything, but always when pushed, and then indifferently

      and with no sign of choice. So we unhesitatingly call them senseless.

      Just so we form our decision upon the deepest of all philosophic

      problems: Is the Kosmos an expression of intelligence rational in its

      inward nature, or a brute external fact pure and simple? If we find

      ourselves, in contemplating it, unable to banish the impression that it

      is a realm of final purposes, that it exists for the sake of something,

      we place intelligence at the heart of it and have a religion. If,

      on the contrary, in surveying its irremediable flux, we can think

      of the present only as so much mere mechanical sprouting from the

      past, occurring with no reference to the future, we are atheists and

      materialists.

      In the lengthy discussions which psychologists have carried on about

      the amount of intelligence displayed by lower mammals, or the amount

      of consciousness involved in the functions of the nerve-centres of

      reptiles, the same test has always been applied: Is the character of

      the actions such that we must believe them to be performed _for the

      sake_ of their result? The result in question, as we shall hereafter

      abundantly see, is as a rule a useful one,--the animal is, on the

      whole, safer under the circumstances for bringing it forth. So far

      the action has a teleological character; but such mere outward

      teleology as this might still be the blind result of _vis a tergo_.

      The growth and movements of plants, the processes of development,

      digestion, secretion, etc., in animals, supply innumerable instances

      of performances useful to the individual which may nevertheless be,

      and by most of us are supposed to be, produced by automatic mechanism.

      The physiologist does not confidently assert conscious intelligence

      in the frog's spinal cord until he has shown that the useful result

      which the nervous machinery brings forth under a given irritation

      _remains the same when the machinery is altered_. If, to take the stock

      instance, the right knee of a headless frog be irritated with acid, the

      right foot will wipe it off. When, however, this foot is amputated,

      the animal will often raise the _left_ foot to the spot and wipe the

      offending material away.

      Pflüger and Lewes reason from such facts in the following way: If the

      first reaction were the result of mere machinery, they say; if that

      irritated portion of the skin discharged the right leg as a trigger

      discharges its own barrel of a shot-gun; then amputating the right

      foot would indeed frustrate the wiping, but would not make the _left_

      leg move. It would simply result in the right stump moving through

      the empty air (which is in fact the phenomenon sometimes observed).

      The right trigger makes no effort to discharge the left barrel if the

      right one be unloaded; nor does an electrical machine ever get restless

      because it can only emit sparks, and not hem pillow-cases like a

      sewing-machine.

      If, on the contrary, the right leg originally moved for the _purpose_

      of wiping the acid, then nothing is more natural than that, when the

      easiest means of effecting that purpose prove fruitless, other means

      should be tried. Every failure must keep the animal in a state of

      disappointment which will lead to all sorts of new trials and devices;

      and tranquillity will not ensue till one of these, by a happy stroke,

      achieves the wished-for end.

      In a similar way Goltz ascribes intelligence to the frog's optic

      lobes and cerebellum. We alluded above to the manner in which a sound

      frog imprisoned in water will discover an outlet to the atmosphere.

      Goltz found that frogs deprived of their cerebral hemispheres would

      often exhibit a like ingenuity. Such a frog, after rising from the

      bottom and finding his farther upward progress checked by the glass

      bell which has been inverted over him, will not persist in butting

      his nose against the obstacle until dead of suffocation, but will

      often re-descend and emerge from under its rim as if, not a definite

      mechanical propulsion upwards, but rather a conscious desire to reach

      the air by hook or crook were the main-spring of his activity. Goltz

      concluded from this that the hemispheres are not the sole seal of

      intellect in frogs. He made the same inference from observing that a

      brainless frog will turn over from his back to his belly when one of

      his legs is sewed up, although the movements required are then very

      different from those excited under normal circumstances by the same

      annoying position. They seem determined, consequently, not merely by

      the antecedent irritant, but by the final end,--though the irritant of

      course is what makes the end desired.

      Another brilliant German author, Liebmann,[2] argues against the

      brain's mechanism accounting for mental action, by very similar

      considerations. A machine as such, he says, will bring forth right

      results when it is in good order, and wrong results if out of repair.

      But both kinds of result flow with equally fatal necessity from their

      conditions. We cannot suppose the clock-work whose structure fatally

      determines it to a certain rate of speed, noticing that this speed is

      too slow or too fast and vainly trying to correct it. Its conscience,

      if it have any, should be as good as that of the best chronometer, for

      both alike obey equally well the same eternal mechanical laws--laws

      from behind. But if the _brain_ be out of order and the man says "Twice

      four are two, instead of Twice four are eight, or else I must go to

      the coal to buy the wharf, instead of I must go to the wharf to buy

      the coal," instantly there arises a consciousness of error. The wrong

      performance, though it obey the same mechanical law as the right, is

      nevertheless condemned,--condemned as contradicting the inner law--the

      law from in front, the purpose or ideal for which the brain _should_

      act, whether it do so or not.

      We need not discuss here whether these writers in drawing their

      conclusion have done justice to all the premises I involved in the

      cases they treat of. We quote their arguments only to show how they

      appeal to the principle that _no actions but such as are done for an

      end, and show a choice of means, can be called indubitable expressions

      of Mind_.

      I shall then adopt this as the criterion by which to circumscribe the

      subject-matter of this work so far as action enters into it. Many

      nervous performances will therefore be unmentioned, as being purely

      physiological. Nor will the anatomy of the nervous system and organs of

      sense be described anew. The reader will find in H. N. Martin's 'Human

      Body,' in G. T. Ladd's 'Physiological Psychology,' and in all the other

      standard Anatomies and Physiologies, a mass of information which we

      must regard as preliminary and take for granted in the present work.[3]

      Of the functions of the cerebral hemispheres, however, since they

      directly subserve consciousness, it will be well to give some little

      account.

      FOOTNOTES:

      [1] _Cf._ Geo. T. Ladd: Elements of Physiological Psychology (1887),

      pt. iii, chap. iii, §§ 9, 12.

      [2] Zur Analysis der Wirklichkeit, p. 489.

      [3] Nothing is easier than to familiarize one's self with the mammalian

      brain. Get a sheep's head, a small saw, chisel, scalpel and forceps

      (all three can best be had from a surgical-instrument maker), and

      unravel its parts either by the aid of a human dissecting book, such as

      Holden's 'Manual of Anatomy,' or by the specific directions _ad hoc_

      given in such books as Foster and Langley's 'Practical Physiology'

      (Macmillan) or Morrell's 'Comparative Anatomy and Dissection of

      Mammalia' (Longmans).

      CHAPTER II.

      THE FUNCTIONS OF THE BRAIN.

      If I begin chopping the foot of a tree, its branches are unmoved by my

      act, and its leaves murmur as peacefully as ever in the wind. If, on

      the contrary, I do violence to the foot of a fellow-man, the rest of

      his body instantly responds to the aggression by movements of alarm or

      defence. The reason of this difference is that the man has a nervous

      system whilst the tree has none; and the function of the nervous system

      is to bring each part into harmonious co-operation with every other.

      The afferent nerves, when excited by some physical irritant, be this

      as gross in its mode of operation as a chopping axe or as subtle as

      the waves of light, conveys the excitement to the nervous centres. The

      commotion set up in the centres does not stop there, but discharges

      itself, if at all strong, through the efferent nerves into muscles

      and glands, exciting movements of the limbs and viscera, or acts of

      secretion, which vary with the animal, and with the irritant applied.

      These acts of response have usually the common character of being of

      service. They ward off the noxious stimulus and support the beneficial

      one; whilst if, in itself indifferent, the stimulus be a sign of some

      distant circumstance of practical importance, the animal's acts are

      addressed to this circumstance so as to avoid its perils or secure its

      benefits, as the case may be. To take a common example, if I hear the

      conductor calling 'All aboard!' as I enter the depot, my heart first

      stops, then palpitates, and my legs respond to the air-waves falling

      on my tympanum by quickening their movements. If I stumble as I run,

      the sensation of falling provokes a movement of the hands towards the

      direction of the fall, the effect of which is to shield the body from

      too sudden a shock. If a cinder enter my eye, its lids close forcibly

      and a copious flow of tears tends to wash it out.

      These three responses to a sensational stimulus differ, however, in

      many respects. The closure of the eye and the lachrymation are quite

      involuntary, and so is the disturbance of the heart. Such involuntary

      responses we know as 'reflex' acts. The motion of the arms to break the

      shock of falling may also be called reflex, since it occurs too quickly

      to be deliberately intended. Whether it be instinctive or whether it

      result from the pedestrian education of childhood may be doubtful; it

      is, at any rate, less automatic than the previous acts, for a man might

      by conscious effort learn to perform it more skilfully, or even to

      suppress it altogether. Actions of this kind, into which instinct and

      volition enter upon equal terms, have been called 'semi-reflex.' The

      act of running towards the train, on the other hand, has no instinctive

      element about it. It is purely the result of education, and is preceded

      by a consciousness of the purpose to be attained and a distinct mandate

      of the will. It is a 'voluntary act.' Thus the animal's reflex and

      voluntary performances shade into each other gradually, being connected

      by acts which may often occur automatically, but may also be modified

      by conscious intelligence.

      An outside observer, unable to perceive the accompanying consciousness,

      might be wholly at a loss to discriminate between the automatic acts

      and those which volition escorted. But if the criterion of mind's

      existence be the choice of the proper means for the attainment of a

      supposed end, all the acts seem to be inspired by intelligence, for

      _appropriateness_ characterizes them all alike. This fact, now, has led

      to two quite opposite theories about the relation to consciousness of

      the nervous functions. Some authors, finding that the higher voluntary

      ones seem to require the guidance of feeling, conclude that over the

      lowest reflexes some such feeling also presides, though it may be a

      feeling of which _we_ remain unconscious. Others, finding that reflex

      and semi-automatic acts may, notwithstanding their appropriateness,

      take place with an unconsciousness apparently complete, fly to the

      opposite extreme and maintain that the appropriateness even of

      voluntary actions owes nothing to the fact that consciousness attends

      them. They are, according to these writers, results of physiological

      mechanism pure and simple. In a near chapter we shall return to this

      controversy again. Let us now look a little more closely at the brain

      and at the ways in which its states may be supposed to condition those

      of the mind.

      THE FROG'S NERVE-CENTRES.

      Both the minute anatomy and the detailed physiology of the brain are

      achievements of the present generation, or rather we may say (beginning

      with Meynert) of the past twenty years. Many points are still obscure

      and subject to controversy; but a general way of conceiving the organ

      has been reached on all hands which in its main feature seems not

      unlikely to stand, and which even gives a most plausible scheme of the

      way in which cerebral and mental operations go hand in hand.

      [Illustration: FIG. 1.--_C H_, cerebral Hemispheres; _O Th_, Optic

      Thalami; _O L_, Optic Lobes; _Cb_, Cerebellum; _M O_, Medulla

      Oblongata; _S C_, Spinal cord.]

      The best way to enter the subject will be to take a lower creature,

      like a frog, and study by the vivisectional method the functions of

      his different nerve-centres. The frog's nerve-centres are figured

      in the accompanying diagram, which needs no further explanation. I

      will first proceed to state what happens when various amounts of the

      anterior parts are removed, in different frogs, in the way in which an

      ordinary student removes them; that is, with no extreme precautions

      as to the purity of the operation. We shall in this way reach a very

      simple conception of the functions of the various centres, involving

      the strongest possible contrast between the cerebral hemispheres and

      the lower lobes. This sharp conception will have didactic advantages,

      for it is often very instructive to start with too simple a formula

      and correct it later on. Our first formula, as we shall later see,

      will have to be softened down somewhat by the results of more careful

      experimentation both on frogs and birds, and by those of the most

      recent observations on dogs, monkeys, and man. But it will put us,

      from the outset, in clear possession of some fundamental notions and

      distinctions which we could otherwise not gain so well, and none of

      which the later more completed view will overturn.

      If, then, we reduce the frog's nervous system to the spinal cord

      alone, by making a section behind the base of the skull, between the

      spinal cord and the medulla oblongata, thereby cutting off the brain

      from all connection with the rest of the body, the frog will still

      continue to live, but with a very peculiarly modified activity. It

      ceases to breathe or swallow; it lies flat on its belly, and does not,

      like a normal frog, sit up on its fore paws, though its hind legs

      are kept, as usual, folded against its body and immediately resume

      this position if drawn out. If thrown on its back, it lies there

      quietly, without turning over like a normal frog. Locomotion and voice

      seem entirely abolished. If we suspend it by the nose, and irritate

      different portions of its skin by acid, it performs a set of remarkable

      'defensive' movements calculated to wipe away the irritant. Thus, if

      the breast be touched, both fore paws will rub it vigorously; if we

      touch the outer side of the elbow, the hind foot of the same side

      will rise directly to the spot and wipe it. The back of the foot will

      rub the knee if that be attacked, whilst if the foot be cut away, the

      stump will make ineffectual movements, and then, in many frogs, a pause

      will come, as if for deliberation, succeeded by a rapid passage of the

      opposite unmutilated foot to the acidulated spot.

      The most striking character of all these movements, after their

      teleological appropriateness, is their precision. They vary, in

      sensitive frogs and with a proper amount of irritation, so little as

      almost to resemble in their machine-like regularity the performances of

      a jumping-jack, whose legs must twitch whenever you pull the string.

      The spinal cord of the frog thus contains arrangements of cells and

      fibres fitted to convert skin irritations into movements of defence. We

      may call it the _centre for defensive movements_ in this animal. We may

      indeed go farther than this, and by cutting the spinal cord in various

      places find that its separate segments are independent mechanisms,

      for appropriate activities of the head and of the arms and legs

      respectively. The segment governing the arms is especially active,

      in male frogs, in the breeding season; and these members alone with

      the breast and back appertaining to them, everything else being cut

      away, will then actively grasp a finger placed between them and remain

      hanging to it for a considerable time.

      The spinal cord in other animals has analogous powers. Even in man

      it makes movements of defence. Paraplegics draw up their legs when

      tickled; and Robin, on tickling the breast of a criminal an hour after

      decapitation, saw the arm and hand move towards the spot. Of the lower

      functions of the mammalian cord, studied so ably by Goltz and others,

      this is not the place to speak.

      If, in a second animal, the cut be made just behind the optic lobes so

      that the cerebellum and medulla oblongata remain attached to the cord,

      then swallowing, breathing, crawling, and a rather enfeebled jumping

      and swimming are added to the movements previously observed.[4] There

      are other reflexes too. The animal, thrown on his back, immediately

      turns over to his belly. Placed in a shallow bowl, which is floated on

      water and made to rotate, he responds to the rotation by first turning

      his head and then waltzing around with his entire body, in the opposite

      direction to the whirling of the bowl. If his support be tilted so that

      his head points downwards, he points it up; he points it down if it be

      pointed upwards, to the right if it be pointed to the left, etc. But

      his reactions do not go farther than these movements of the head. He

      will not, like frogs whose thalami are preserved, climb up a board if

      the latter be tilted, but will slide off it to the ground.

      If the cut be made on another frog between the thalami and the optic

      lobes, the locomotion both on land and water becomes quite normal, and,

      in addition to the reflexes already shown by the lower centres, he

      croaks regularly whenever he is pinched under the arms. He compensates

      rotations, etc., by movements of the head, and turns over from his

      back; but still drops off his tilted board. As his optic nerves are

      destroyed by the usual operation, it is impossible to say whether he

      will avoid obstacles placed in his path.

      When, finally, a frog's cerebral hemispheres alone are cut off by a

      section between them and the thalami which preserves the latter, an

      unpractised observer would not at first suspect anything abnormal

      about the animal. Not only is he capable, on proper instigation, of

      all the acts already described, but he guides himself by sight, so

      that if an obstacle be set up between him and the light, and he be

      forced to move forward, he either jumps over it or swerves to one

      side. He manifests sexual passion at the proper season, and, unlike an

      altogether brainless frog, which embraces anything placed between his

      arms, postpones this reflex act until a female of his own species is

      provided. Thus far, as aforesaid, a person unfamiliar with frogs might

      not suspect a mutilation; but even such a person would soon remark the

      almost entire absence of spontaneous motion--that is, motion unprovoked

      by any _present_ incitation of sense. The continued movements of

      swimming, performed by the creature in the water, seem to be the fatal

      result of the contact of that fluid with its skin. They cease when a

      stick, for example, touches his hands. This is a sensible irritant

      towards which the feet are automatically drawn by reflex action, and

      on which the animal remains sitting. He manifests no hunger, and will

      suffer a fly to crawl over his nose unsnapped at. Fear, too, seems

      to have deserted him. In a word, he is an extremely complex machine

      whose actions, so far as they go, tend to self-preservation; but still

      a _machine_, in this sense--that it seems to contain no incalculable

      element. By applying the right sensory stimulus to him we are almost

      as certain of getting a fixed response as an organist is of hearing a

      certain tone when he pulls out a certain stop.

      But now if to the lower centres we add the cerebral hemispheres,

      or if, in other words, we make an intact animal the subject of our

      observations, all this is changed. In addition to the previous

      responses to present incitements of sense, our frog now goes through

      long and complex acts of locomotion _spontaneously_, or as if moved by

      what in ourselves we should call an idea. His reactions to outward

      stimuli vary their form, too. Instead of making simple defensive

      movements with his hind legs like a headless frog if touched, or of

      giving one or two leaps and then sitting still like a hemisphereless

      one, he makes persistent and varied efforts at escape, as if, not the

      mere contact of the physiologist's hand, but the notion of danger

      suggested by it were now his spur. Led by the feeling of hunger, too,

      he goes in search of insects, fish, or smaller frogs, and varies his

      procedure with each species of victim. The physiologist cannot by

      manipulating him elicit croaking, crawling up a board, swimming or

      stopping, at will. His conduct has become incalculable. We can no

      longer foretell it exactly. Effort to escape is his dominant reaction,

      but he _may_ do anything else, even swell up and become perfectly

      passive in our hands.

            *      *      *      *      *

      Such are the phenomena commonly observed, and such the impressions

      which one naturally receives. Certain general conclusions follow

      irresistibly. First of all the following:

      _The acts of all the centres involve the use of the same muscles._ When

      a headless frog's hind leg wipes the acid, he calls into play all the

      leg-muscles which a frog with his full medulla oblongata and cerebellum

      uses when he turns from his back to his belly. Their contractions are,

      however, _combined_ differently in the two cases, so that the results

      vary widely. We must consequently conclude that specific arrangements

      of cells and fibres exist in the cord for wiping, in the medulla for

      turning over, etc. Similarly they exist in the thalami for jumping

      over seen obstacles and for balancing the moved body; in the optic

      lobes for creeping backwards, or what not. But in the hemispheres,

      since the presence of these organs _brings no new elementary form of

      movement_ with it, but only _determines differently the occasions_

      on which the movements shall occur, making the usual stimuli less

      fatal and machine-like; we need suppose no such machinery _directly_

      co-ordinative of muscular contractions to exist. We may rather

      assume, when the mandate for a wiping-movement is sent forth by the

      hemispheres, that a current goes straight to the wiping-arrangement in

      the spinal cord, exciting this arrangement as a whole. Similarly, if an

      intact frog wishes to jump over a stone which he sees, all he need do

      is to excite from the hemispheres the jumping-centre in the thalami or

      wherever it may be, and the latter will provide for the details of the

      execution. It is like a general ordering a colonel to make a certain

      movement, but not telling him how it shall be done.[5]

      _The same muscle, then, is repeatedly represented at different

      heights;_ and at each it enters into a different combination with other

      muscles to co-operate in some special form of concerted movement.

      _At each height the movement is discharged by some particular form

      of sensorial stimulus._ Thus in the cord, the skin alone occasions

      movements; in the upper part of the optic lobes, the eyes are added;

      in the thalami, the semi-circular canals would seem to play a part;

      whilst the stimuli which discharge the hemispheres would seem not so

      much to be elementary sorts of sensation, as groups of sensations

      forming determinate _objects_ or _things. Prey_ is not pursued nor are

      _enemies_ shunned by ordinary hemisphereless frogs. Those reactions

      upon complex circumstances which we call instinctive rather than

      reflex, are already in this animal dependent on the brain's highest

      lobes, and still more is this the case with animals higher in the

      zoological scale.

      The results are just the same if, instead of a frog, we take a pigeon,

      and cut out his hemispheres as they are ordinarily cut out for a

      lecture-room demonstration. There is not a movement natural to him

      which this brainless bird cannot perform if expressly excited thereto;

      only the inner promptings seem deficient, and when left to himself

      he spends most of his time crouched on the ground with his head sunk

      between his shoulders as if asleep.

      GENERAL NOTION OF HEMISPHERES.

      All these facts lead us, when we think about them, to some such

      explanatory conception as this: _The lower centres act from present

      sensational stimuli alone; the hemispheres act from perceptions and

      considerations,_ the sensations which they may receive serving only as

      suggesters of these. But what are perceptions but sensations grouped

      together? and what are considerations but expectations, in the fancy,

      of sensations which will be felt one way or another according as action

      takes this course or that? If I step aside on seeing a rattlesnake,

      from considering how dangerous an animal he is, the mental materials

      which constitute my prudential reflection are images more or less vivid

      of the movement of his head, of a sudden pain in my leg, of a state of

      terror, a swelling of the limb, a chill, delirium, unconsciousness,

      etc., etc., and the ruin of my hopes. But all these images are

      constructed out of my past experiences. They are _reproductions_ of

      what I have felt or witnessed. They are, in short, _remote_ sensations;

      and the _difference between the hemisphereless animal and the whole

      one_ may be concisely expressed by saying that the _one obeys absent,

      the other only present, objects._

      The hemispheres would then seem to be _the seat of memory_. Vestiges

      of past experience must in some way be stored up in them, and must,

      when aroused by present stimuli, first appear as representations of

      distant goods and evils; and then must discharge into the appropriate

      motor channels for warding off the evil and securing the benefits of

      the good. If we liken the nervous currents to electric currents, we

      can compare the nervous system, _C_, below the hemispheres to a direct

      circuit from sense-organ to muscle along the line _S ... C ... M_ of

      Fig. 2. The hemisphere, _H_, adds the long circuit or loop-line through

      which the current may pass when for any reason the direct line is not

      used.

      Thus, a tired wayfarer on a hot day throws himself on the damp earth

      beneath a maple-tree. The sensations of delicious rest and coolness

      pouring themselves through the direct line would naturally discharge

      into the muscles of complete extension: he would abandon himself

      to the dangerous repose. But the loop-line being open, part of the

      current is drafted along it, and awakens rheumatic or catarrhal

      reminiscences, which prevail over the instigations of sense, and

      make the man arise and pursue his way to where he may enjoy his rest

      more safely. Presently we shall examine the manner in which the

      hemispheric loop-line may be supposed to serve as a reservoir for such

      reminiscences as these. Meanwhile I will ask the reader to notice some

      corollaries of its being such a reservoir.

      [Illustration: FIG. 2.]

      First, no animal without it can deliberate, pause, postpone, nicely

      weigh one motive against another, or compare. Prudence, in a word,

      is for such a creature an impossible virtue. Accordingly we see that

      nature removes those functions in the exercise of which prudence is

      a virtue from the lower centres and hands them over to the cerebrum.

      Wherever a creature has to deal with complex features of the

      environment, prudence is a virtue. The higher animals have so to deal;

      and the more complex the features, the higher we call the animals. The

      fewer of his acts, then, can _such_ an animal perform without the help

      of the organs in question. In the frog many acts devolve wholly on the

      lower centres; in the bird fewer; in the rodent fewer still; in the dog

      very few indeed; and in apes and men hardly any at all.

      The advantages of this are obvious. Take the prehension of food as an

      example and suppose it to be a reflex performance of the lower centres.

      The animal will be condemned fatally and irresistibly to snap at it

      whenever presented, no matter what the circumstances may be; he can no

      more disobey this prompting than water can refuse to boil when a fire

      is kindled under the pot. His life will again and again pay the forfeit

      of his gluttony. Exposure to retaliation, to other enemies, to traps,

      to poisons, to the dangers of repletion, must be regular parts of his

      existence. His lack of all thought by which to weigh the danger against

      the attractiveness of the bait, and of all volition to remain hungry

      a little while longer, is the direct measure of his lowness in the

      mental scale. And those fishes which, like our cunners and sculpins,

      are no sooner thrown back from the hook into the water, than they

      automatically seize the hook again, would soon expiate the degradation

      of their intelligence by the extinction of their type, did not their

      exaggerated fecundity atone for their imprudence. Appetite and the acts

      it prompts have consequently become in all higher vertebrates functions

      of the cerebrum. They disappear when the physiologist's knife has left

      the subordinate centres alone in place. The brainless pigeon will

      starve though left on a corn-heap.

      Take again the sexual function. In birds this devolves exclusively

      upon the hemispheres. When these are shorn away the pigeon pays no

      attention to the billings and cooings of its mate. And Goltz found that

      a bitch in heat would excite no emotion in male dogs who had suffered

      large loss of cerebral tissue. Those who have read Darwin's 'Descent of

      Man' know what immense importance in the amelioration of the breed in

      birds this author ascribes to the mere fact of sexual selection. The

      sexual act is not performed until every condition of circumstance and

      sentiment is fulfilled, until time, place, and partner all are fit. But

      in frogs and toads this passion devolves on the lower centres. They

      show consequently a machine-like obedience to the present incitement of

      sense, and an almost total exclusion of the power of choice. Copulation

      occurs _per fas aut nefas_, occasionally between males, often with dead

      females, in puddles exposed on the highway, and the male may be cut in

      two without letting go his hold. Every spring an immense sacrifice of

      batrachian life takes place from these causes alone.

      No one need be told how dependent all human social elevation is upon

      the prevalence of chastity. Hardly any factor measures more than this

      the difference between civilisation and barbarism. Physiologically

      interpreted, chastity means nothing more than the fact that present

      solicitations of sense are overpowered by suggestions of æsthetic and

      moral fitness which the circumstances awaken in the cerebrum; and that

      upon the inhibitory or permissive influence of these alone action

      directly depends.

      Within the psychic life due to the cerebrum itself the same general

      distinction obtains, between considerations of the more immediate

      and considerations of the more remote. In all ages the man whose

      determinations are swayed by reference to the most distant ends has

      been held to possess the highest intelligence. The tramp who lives

      from hour to hour; the bohemian whose engagements are from day to day;

      the bachelor who builds but for a single life;

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