Chapter XI: Part 11

Professor Haeckel proposes to break up the vertebrate sub-kingdom, first, into the two provinces of _Leptocardia_ and _Pachycardia; Amphioxus_ being in the former, and all other vertebrates in the latter division. The _Pachycardia_ are then divided into _Monorhina_, which contains the Cyclostome fishes, distinguished by their single nasal aperture; and _Amphirhina_, comprising the other _Vertebrata_, which have two nasal apertures. These are further subdivided into _Anamnia (Pisces, Dipneusta, Amphibia)_ and _Amniota (Reptilia, Aves, Mammalia)_. This classification undoubtedly expresses many of the most important facts in vertebrate structure in a clear and compendious way; whether it is the best that can he adopted remains to be seen.

With much reason the Lemurs are removed altogether from the _Primates_, under the name of _Prosimiae_. But I am surprised to find the _Sirenia_ left in one group with the _Cetacea_, and the _Plesiosauria_ with the _Ichthyosauria_; the ordinal distinctness of these having, to my mind, been long since fully established.

V. In Professor Haeckel's speculations on Phylogeny, or the genealogy of animal forms, there is much that is profoundly interesting, and his suggestions are always supported by sound knowledge and great ingenuity. Whether one agrees or disagrees with him, one feels that he has forced the mind into lines of thought in which it is more profitable to go wrong than to stand still.

To put his views into a few words, he conceives that all forms of life originally commenced as _Monera_, or simple particles of protoplasm; and that these _Monera_ originated from not-living matter. Some of the _Monera_ acquired tendencies towards the Protistic, others towards the Vegetal, and others towards the Animal modes of life. The last became animal _Monera_. Some of the animal _Monera_ acquired a nucleus, and became amoeba-like creatures; and, out of certain of these, ciliated infusorium-like animals were developed. These became modified into two stirpes: A, that of the worms; and B, that of the sponges. The latter by progressive modification gave rise to all the _Coelenterata_; the former to all other animals. But A soon broke up into two principal stirpes, of which one, _a_, became the root of the _Annelida, Echinodermata_, and _Arthropoda_, while the other, _b_, gave rise to the _Polyzoa_ and _Ascidioida_, and produced the two remaining stirpes of the _Vertebrata_ and the _Mollusca_.

Perhaps the most startling proposition of all those which Professor Haeckel puts before us is that which he bases upon Kowalewsky's researches into the development of _Amphioxus_ and of the _Ascidioida_, that the origin of the _Vertebrata_ is to be sought in an Ascidioid form. Goodsir long ago insisted upon the resemblance between _Amphioxus_ and the Ascidians; but the notion of a genetic connection between the two, and especially the identification of the notochord of the _Vertebrate_ with the axis of the caudal appendage of the larva of the Ascidian, is a novelty which, at first, takes one's breath away. I must confess, however, that the more I have pondered over it, the more grounds appear in its favour, though I am not convinced that there is any real parallelism between the mode of development of the ganglion of the _Ascidian_ and that of the _Vertebrate_ cerebro-spinal axis.

The hardly less startling hypothesis that the _Echinoderms_ are coalesced worms, on the other hand, appears to be open to serious objection. As a matter of anatomy, it does not seem to me to correspond with fact; for there is no worm with a calcareous skeleton, nor any which has a band-like ventral nerve, superficial to which lies an ambulacral vessel. And, as a question of development, the formation of the radiate _Echinoderm_ within its vermiform larva seems to me to be analogous to the formation of a radiate Medusa upon a Hydrozoic stock. But a Medusa is surely not the result of the coalescence of as many organisms as it presents morphological segments.

Professor Haeckel adduces the fossil _Crossopodia_ and _Phyllodocites_ as examples of the Annelidan forms, by the coalescence of which the Echinoderms may have been produced; but, even supposing the resemblance of these worms to detached starfish arms to be perfect, it is possible that they may be the extreme term, and not the commencement, of Echinoderm development. A pentacrinoid Echinoderm, with a complete jointed stalk, is developed within the larva of _Antedon_. Is it not possible that the larva of _Crossopodia_ may have developed a vermiform Echinoderm?

With respect to the Phylogeny of the _Arthropoda_, I find myself disposed to take a somewhat different view from that of Professor Haeckel. He assumes that the primary stock of the whole group was a crustacean, having that _Nauplius_ form in which Fritz Müller has shown that so many _Crustacea_ commence their lives. All the _Entomostraca_ arose by the modification of some one or other of these Naupliform "_Archicarida_." Other _Archicarida_ underwent a further metamorphosis into a _Zoaea_-form. From some of these "_Zoeopoda_" arose all the remaining Malacostracous _Crustacea_; while, from others, was developed some form analogous to the existing _Galeodes_, out of which proceeded, by gradual differentiation, all the _Myriapoda, Arachnida,_ and _Insecta_.

I should, be disposed to interpret the facts of the embryological history and of the anatomy of the _Arthropoda_ in a different manner. The _Copepoda_, the _Ostracoda_, and the _Branchiopoda_ are the _Crustacea_ which have departed least from the embryonic or _Nauplius_-forms; and, of these, I imagine that the _Copepoda_ represent the hypothetical _Archicarida_ most closely. _Apus_ and _Sapphirina_ indicate the relations of these Archaeocarids with the _Trilobita_, and the _Eurypterida_ connect the _Trilobita_ and the _Copepoda_ with the _Xiphosura_. But the _Xiphosura_ have such close morphological relations with the _Arachnida_, and especially with the oldest known Arachnidan, _Scorpio_, that I cannot doubt the existence of a genetic connection between the two groups. On the other hand, the _Branchiopoda_ do, even at the present day, almost pass into the true _Podophthalmia_, by _Nebalia_. By the _Trilobita_, again, the _Archicarida_ are connected with such _Edriophthalmia_ as _Serolis_. The _Stomapoda_ are extremely modified _Edriophthalmia_ of the amphipod type. On the other side, the _Isopoda_ lead to the _Myriapoda_, and the latter to the _Insecta_. Thus the Arthropod phylum, which suggests itself to me, is that the branches of the _Podophthalmia_, of the _Insecta_ (with the _Myriapoda_), and of the _Arachnida_, spring separately and distinctly from the Archaeocarid root--and that the _Zoaea_-forms occur only at the origin of the Podophthalmous branch.

The phylum of the _Vertebrata_ is the most interesting of all, and is admirably discussed by Professor Haeckel. I can note only a few points which seem to me to be open to discussion. The _Monorhina_, having been developed out of the _Leptocardia_, gave rise, according to Professor Haeckel, to a shark-like form, which was the common stock of all the _Amphirhina_. From this "Protamphirhine" were developed, in divergent lines, the true Sharks, Rays, and _Chimaerae_; the Ganoids, and the _Dipneusta_. The _Teleostei_ are modified _Ganoidei_. The _Dipneusta_ gave rise to the _Amphibia_, which are the root of all other _Vertebrata_, inasmuch as out of them were developed the first _Vertebrata_ provided with an amnion, or the _Protamniota_. The _Protamniota_ split up into two stems, one that of the _Mammalia_, the other common to _Reptilia_ and _Aves_.

The only modification which it occurs to me to suggest in this general view of the Phylogeny of the _Vertebrata_ is, that the "Protamphirhine" was possibly more ganoid than shark-like. So far as our present information goes the Ganoids are as old as the Sharks; and it is very interesting to observe that the remains of the oldest Ganoids, _Cephalaspis_ and _Pteraspis_, have as yet displayed no trace of jaws. It is just possible that they may connect the _Monorhina_, with the Sturgeons among the _Amphirhina_. On the other hand, the Crossopterygian Ganoids exhibit the closest connection with _Lepidosiren_, and thereby with the _Amphibia_. It should not be forgotten that the development of the Lampreys exhibits curious points of resemblance with that of the _Amphibia_, which are absent in the Sharks and Rays. Of the development of the _Ganoidei_ we have unfortunately no knowledge, but their brains and their reproductive organs are more amphibian than are those of the Sharks.

On the whole, I am disposed to think that the direct stem of ascent from the _Monorhina_ to the _Amphibia_ is formed by the Ganoids and the Mudfishes; while the Osseous fishes and the Sharks are branches in different directions from this stem.

What the _Protamniota_ were like, I do not suppose any one is in a position to say, but I cannot think that the thoroughly Lacertian _Protorosaurus_ had anything to do with them. The reptiles which are most amphibian in their characters, and therefore, probably, most nearly approach the _Protamniota_, are the _Ichthyosauria_ and the _Chelonia_.

That the _Didelphia_ were developed out of some ornithodelphous form, as Professor Haeckel supposes, seems to be unquestionable; but the existing Opossums and Kangaroos are certainly extremely modified and remote from their ancestors the "_Prodidelphia_," of which we have not, at present the slightest knowledge. The mode of origin of the _Monodelphia_ from these is a very difficult problem, for the most part left open by Professor Haeckel. He considers the _Prosimiae_, or Lemurs, to be the common stock of the _Deciduata_, and the _Cetacea_ (with which he includes the _Sirenia_) to be modified _Ungulata_. As regards the latter question, I have little doubt that the _Sirenia_ connect the _Ungulata_ with the _Proboscidea_; and none, that the _Cetacea_ are extremely modified _Carnivora_. The passage between the Seals and the _Cetacea_ by _Zeuglodon_ is complete. I also think that there is much to be said for the opinion, that the _Insectivora_ represent the common stock of the _Primates_ (which passed into them by the _Prosimiae_), the _Cheiroptera_, the _Rodentia_, and the _Carnivora_. And I am greatly disposed to look for the common root of all the _Ungulata_, as well, in some ancient non-deciduate Mammals which were more like _Insectivora_ than anything else. On the other hand, the _Edentata_ appear to form a series by themselves.

The latter part of this notice of the _Natürliche Schöpfungs-Geschichte_, brings so strongly into prominence the points of difference between its able author and myself, that I do not like to conclude without reminding the reader of my entire concurrence with the general tenor and spirit of the work, and of my high estimate of its value.

XII.

BISHOP BERKELEY ON THE METAPHYSICS OF SENSATION.[1]

Professor Fraser has earned the thanks of all students of philosophy for the conscientious labour which he has bestowed upon his new edition of the works of Berkeley; in which, for the first time, we find collected together every thought which can be traced to the subtle and penetrating mind of the famous Bishop of Cloyne; while the "Life and Letters" will rejoice those who care less for the idealist and the prophet of tar-water, than for the man who stands out as one of the noblest and purest figures of his time: that Berkeley from whom the jealousy of Pope did not withhold a single one of all "the virtues under heaven;" nor the cynicism of Swift, the dignity of "one of the first men of the kingdom for learning and virtue;" the man whom the pious Atterbury could compare to nothing less than an angel; and whose personal influence and eloquence filled the Scriblerus Club and the House of Commons with enthusiasm for the evangelization of the North American Indians; and even led Sir Robert Walpole to assent to the appropriation of public money to a scheme which was neither business nor bribery.[2]

[Footnote 1: "The Works of George Berkeley, D.D., formerly Bishop of Cloyne, including many of his Works hitherto unpublished, with Preface, Annotations, his Life and Letters, and an Account of his Philosophy." By A.C. Fraser. Four vols. Oxford: Clarendon Press. 1871.]

[Footnote 2: In justice to Sir Robert, however, it is proper to remark that he declared afterwards, that he gave his assent to Berkeley's scheme for the Bermuda University only because he thought the House of Commons was sure to throw it out.]

Hardly any epoch in the intellectual history of England is more remarkable in itself, or possesses a greater interest for us in these latter days, than that which coincides broadly with the conclusion of the seventeenth and the opening of the eighteenth century.

The political fermentation of the preceding age was gradually working itself out; domestic peace gave men time to think; and the toleration won by the party of which Locke was the spokesman, permitted a freedom of speech and of writing such as has rarely been exceeded in later times.

Fostered by these circumstances, the great faculty for physical and metaphysical inquiry, with which the people of our race are naturally endowed, developed itself vigorously; and at least two of its products have had a profound and a permanent influence upon the subsequent course of thought in the world. The one of these was English Freethinking; the other, the Theory of Gravitation.

Looking back to the origin of the intellectual impulses of which these were the results, we are led to Herbert, to Hobbes, to Bacon; and to one who stands in advance of all these, as the most typical man of his time--Descartes. It is the Cartesian doubt--the maxim that assent may properly be given to no propositions but such as are perfectly clear and distinct--which, becoming incarnate, so to speak, in the Englishmen, Anthony Collins, Toland, Tindal, Woolston, and in the wonderful Frenchman, Pierre Bayle, reached its final term in Hume.

And, on the other hand, although the theory of Gravitation set aside the Cartesian vortices--yet the spirit of the "Principes de Philosophie" attained its apotheosis when Newton demonstrated all the host of heaven to be but the elements of a vast mechanism, regulated by the same laws as those which govern the falling of a stone to the ground. There is a passage in the preface to the first edition of the "Principia" which shows that Newton was penetrated, as completely as Descartes, with the belief that all the phenomena of nature are expressible in terms of matter and motion.

"Would that the rest of the phenomena of nature could be deduced by a like kind of reasoning from mechanical principles. For many circumstances lead me to suspect that all these phenomena may depend upon certain forces, in virtue of which the particles of bodies, by causes not yet known, are either mutually impelled against one another and cohere into regular figures, or repel and recede from one another; which forces being unknown, philosophers have as yet explored nature in vain. But I hope that, either by this method of philosophizing, or by some other and better, the principles here laid down may throw some light upon the matter."[1]

[Footnote 1: "Utinam caetera naturae phaenomena ex principiis mechanicis, eodem argumentandi genere, derivare licet. Nam multa me movent, ut nonnihil suspicer ca omnia ex viribus quibusdam pendere posse, quibus corporum particulae, per causas nondum cognitas, vel in se mutuo impelluntur et secundum figuras regulares cohaerent vel ab invicem fugantur et reced ent: quibus viribus ignotis, Philosophi hactenus Naturam frustra tentarunt. Spero autem quod vel huic philosophandi modo, vel veriori, alicui, principia hic posita lucem aliquam praebebunt."--Preface to First Edition of _Principia_, May 8, 1686.]

But the doctrine that all the phenomena of nature are resolvable into mechanism is what people have agreed to call "materialism;" and when Locke and Collins maintained that matter may possibly be able to think, and Newton himself could compare infinite space to the sensorium of the Deity, it was not wonderful that the English philosophers should be attacked as they were by Leibnitz in the famous letter to the Princess of Wales, which gave rise to his correspondence with Clarke.[1]

[Footnote 1: "Collection of Papers which passed between the late learned Mr. Leibnitz and Dr. Clarke."--1717.]

"1. Natural religion itself seems to decay [in England] very much. Many will have human souls to be material; others make God Himself a corporeal Being.

"2. Mr. Locke and his followers are uncertain, at least, whether the soul be not material and naturally perishable.

"3. Sir Isaac Newton says that space is an organ which God makes use of to perceive things by. But if God stands in need of any organ to perceive things by, it will follow that they do not depend altogether upon Him, nor were produced by Him.

"4. Sir Isaac Newton and his followers have also a very odd opinion concerning the work of God. According to their doctrine, God Almighty wants to wind up His watch from time to time; otherwise it would cease to move.[1] He had not, it seems, sufficient foresight to make it a perpetual motion. Nay, the machine of God's making is so imperfect, according to these gentlemen, that He is obliged to clean it now and then by an extraordinary concourse, and even to mend it as a clockmaker mends his work."

[Footnote 1: Goethe seems to have had this saying of Leibnitz in his mind when he wrote his famous lines--

"Was wär' ein Gott der nur von aussen stiesse Im Kreis das All am Finger laufen liesse."]

It is beside the mark, at present, to inquire how far Leibnitz paints a true picture, and how far he is guilty of a spiteful caricature of Newton's views in these passages; and whether the beliefs which Locke is known to have entertained are consistent with the conclusions which may logically be drawn from some parts of his works. It is undeniable that English philosophy in Leibnitz's time had the general character which he ascribes to it. The phenomena of nature were held to be resolvable into the attractions and the repulsions of particles of matter; all knowledge was attained through the senses; the mind antecedent to experience was a _tabula rasa_. In other words, at the commencement of the eighteenth century, the character of speculative thought in England was essentially sceptical, critical, and materialistic. Why "materialism" should be more inconsistent with the existence of a Deity, the freedom of the will, or the immortality of the soul, or with any actual or possible system of theology, than "idealism," I must declare myself at a loss to divine. But in the year 1700 all the world appears to have been agreed, Tertullian notwithstanding, that materialism necessarily leads to very dreadful consequences. And it was thought that it conduced to the interests of religion and morality to attack the materialists with all the weapons that came to hand. Perhaps the most interesting controversy which arose out of these questions is the wonderful triangular duel between Dodwell, Clarke, and Anthony Collins, concerning the materiality of the soul, and--what all the disputants considered to be the necessary consequence of its materiality--its natural mortality. I do not think that anyone can read the letters which passed between Clarke and Collins, without admitting that Collins, who writes with wonderful power and closeness of reasoning, has by far the best of the argument, so far as the possible materiality of the soul goes; and that, in this battle, the Goliath of Freethinking overcame the champion of what was considered Orthodoxy.

But in Dublin, all this while, there was a little David practising his youthful strength upon the intellectual lions and bears of Trinity College. This was George Berkeley, who was destined to give the same kind of development to the idealistic side of Descartes' philosophy, that the Freethinkers had given to its sceptical side, and the Newtonians to its mechanical side.

Berkeley faced the problem boldly. He said to the materialists: "You tell me that all the phenomena of nature are resolvable into matter and its affections. I assent to your statement, and now I put to you the further question, 'What is matter?' In answering this question you shall be bound by your own conditions; and I demand, in the terms of the Cartesian axiom, that in turn you give your assent only to such conclusions as are perfectly clear and obvious."

It is this great argument which is worked out in the "Treatise concerning the Principles of Human Knowledge," and in those "Dialogues between Hylas and Philonous," which rank among the most exquisite examples of English style, as well as among the subtlest of metaphysical writings; and the final conclusion of which is summed up in a passage remarkable alike for literary beauty and for calm audacity of statement.

"Some truths there are so near and obvious to the mind that
a man need only open his eyes to see them. Such I take this
important one to be, viz., that all the choir of heaven and
furniture of the earth--in a word, all those bodies which
compose the mighty frame of the world--have not any substance
without a mind; that their being is to be perceived or known;
that consequently, so long as they are not actually perceived
by me, or do not exist in my mind or that of any other created
spirit, they must either have no existence at all or else
subsist in the mind of some eternal spirit; it being
perfectly unintelligible, and involving all the absurdity
of abstraction, to attribute to any single part of them an
existence independent of a spirit."[1]

[Footnote 1: "Treatise concerning the Principles of Human Knowledge," Part I. § 6.]

Doubtless this passage sounds like the acme of metaphysical paradox, and we all know that "coxcombs vanquished Berkeley with a grin;" while common-sense folk refuted him by stamping on the ground, or some such other irrelevant proceeding. But the key to all philosophy lies in the clear apprehension of Berkeley's problem--which is neither more nor less than one of the shapes of the greatest of all questions, "What are the limits of our faculties?" And it is worth any amount of trouble to comprehend the exact nature of the argument by which Berkeley arrived at his results, and to know by one's own knowledge the great truth which he discovered--that the honest and rigorous following up of the argument which leads us to materialism, inevitably carries us beyond it.

Suppose that I accidentally prick my finger with a pin. I immediately become aware of a condition of my consciousness--a feeling which I term pain. I have no doubt whatever that the feeling is in myself alone; and if anyone were to say that the pain I feel is something which inheres in the needle, as one of the qualities of the substance of the needle, we should all laugh at the absurdity of the phraseology. In fact, it is utterly impossible to conceive pain except as a state of consciousness.

Hence, so far as pain is concerned, it is sufficiently obvious that Berkeley's phraseology is strictly applicable to our power of conceiving its existence--"its being is to be perceived or known," and "so long as it is not actually perceived by me, or does not exist in my mind, or that of any other created spirit, it must either have no existence at all, or else subsist in the mind of some eternal spirit."

So much for pain. Now let us consider an ordinary sensation. Let the point of the pin be gently rested upon the skin, and I become aware of a feeling or condition of consciousness quite different from the former--the sensation of what I call "touch." Nevertheless this touch is plainly just as much in myself as the pain was. I cannot for a moment conceive this something which I call touch as existing apart from myself, or a being capable of the same feelings as myself. And the same reasoning applies to all the other simple sensations. A moment's reflection is sufficient to convince one that the smell, and the taste, and the yellowness, of which we become aware when an orange is smelt, tasted, and seen, are as completely states of our consciousness as is the pain which arises if the orange happens to be too sour. Nor is it less clear that every sound is a state of the consciousness of him who hears it. If the universe contained only blind and deaf beings, it is impossible for us to imagine but that darkness and silence should reign everywhere.

It is undoubtedly true, then, of all the simple sensations that, as Berkeley says, their "_esse_ is _percipi_"--their being is to be "perceived or known." But that which perceives, or knows, is mind or spirit; and therefore that knowledge which the senses give us is, after all, a knowledge of spiritual phenomena.

All this was explicitly or implicitly admitted, and, indeed, insisted upon, by Berkeley's contemporaries, and by no one more strongly than by Locke, who terms smells, tastes, colours, sounds, and the like, "secondary qualities," and observes, with respect to these "secondary qualities," that "whatever reality we by mistake attribute to them [they] are in truth nothing in the objects themselves."

And again: "Flame is denominated hot and light; snow, white and cold; and manna, white and sweet, from the ideas they produce in us; which qualities are commonly thought to be the same in these bodies; that those ideas are in us, the one the perfect resemblance of the other as they are in a mirror; and it would by most men be judged very extravagant if one should say otherwise. And yet he that will consider that the same fire that at one distance produces in us the sensation of warmth, does at a nearer approach produce in us the far different sensation of pain, ought to bethink himself what reason he has to say that his idea of warmth, which was produced in him by the fire, is actually in the fire; and his idea of pain which the same fire produced in him in the same way, is not in the fire. Why are whiteness and coldness in snow, and pain not, when it produces the one and the other idea in us; and can do neither but by the bulk, figure, number, and motion of its solid parts?"[1]

[Footnote 1: Locke, "Human Understanding," Book II. chap. viii. §§ 14, 15.]

Thus far then materialists and idealists are agreed. Locke and Berkeley, and all logical thinkers who have succeeded them, are of one mind about secondary qualities--their being is to be perceived or known--their materiality is, in strictness, a spirituality.

But Locke draws a great distinction between the secondary qualities of matter, and certain others which he terms "primary qualities." These are extension, figure, solidity, motion and rest, and number; and he is as clear that these primary qualities exist independently of the mind, as he is that the secondary qualities have no such existence.

"The particular bulk, number, figure, and motion of the parts
of fire and snow are really in them, whether anyone's senses
perceive them or not, and therefore they may be called real
qualities, because they really exist in those bodies; but
light, heat, whiteness, or coldness, are no more really in
them, than sickness, or pain, is in manna. Take away the
sensation of them; let not the eyes see light or colours, nor
the ears hear sounds; let the palate not taste, nor the nose
smell; and all colours, tastes, odours and sounds, as they are
such particular ideas, vanish and cease, and are reduced to
their causes, i.e. bulk, figure, and motion of parts.

"18. A piece of manna of sensible bulk is able to produce in
us the idea of a round or square figure; and, by being removed
from one place to another, the idea of motion. This idea of
motion represents it as it really is in the manna moving; a
circle and square are the same, whether in idea or existence,
in the mind or in the manna; and thus both motion and figure
are really in the manna, whether we take notice of them or no:
this everybody is ready to agree to."

So far as primary qualities are concerned, then, Locke is as thoroughgoing a realist as St. Anselm. In Berkeley, on the other hand, we have as complete a representative of the nominalists and conceptualists--an intellectual descendant of Roscellinus and of Abelard. And by a curious irony of fate, it is the nominalist who is, this time, the champion of orthodoxy, and the realist that of heresy.

Once more let us try to work out Berkeley's principles for ourselves, and inquire what foundation there is for the assertion that extension, form, solidity, and the other "primary qualities," have an existence apart from mind. And for this purpose let us recur to our experiment with the pin.

It has been seen that when the finger is pricked with a pin, a state of consciousness arises which we call pain; and it is admitted that this pain is not a something which inheres in the pin, but a something which exists only in the mind, and has no similitude elsewhere.

But a little attention will show that this state of consciousness is accompanied by another, which can by no effort be got rid of. I not only have the feeling, but the feeling is localized. I am just as certain that the pain is in my finger, as I am that I have it at all. Nor will any effort of the imagination enable me to believe that the pain is not in my finger.

And yet nothing is more certain than that it is not, and cannot be, in the spot in which I feel it, nor within a couple of feet of that spot. For the skin of the finger is connected by a bundle of fine nervous fibres, which run up the whole length of the arm, with the spinal marrow and brain, and we know that the feeling of pain caused by the prick of a pin is dependent on the integrity of those fibres. After they have been cut through close to the spinal cord, no pain will be felt, whatever injury is done to the finger; and if the ends which remain in connection with the cord be pricked, the pain which arises will appear to have its seat in the finger just as distinctly as before. Nay, if the whole arm be cut off, the pain which arises from pricking the nerve stump will appear to be seated in the fingers, just as if they were still connected with the body.

It is perfectly obvious, therefore, that the localization of the pain at the surface of the body is an act of the mind. It is an _extradition_ of that consciousness, which has its seat in the brain, to a definite point of the body--which takes place without our volition, and may give rise to ideas which are contrary to fact. We might call this extradition of consciousness a reflex feeling, just as we speak of a movement which is excited apart from, or contrary to, our volition, as a reflex motion. Locality is no more in the pin than pain is; of the former, as of the latter, it is true that "its being is to be perceived," and that its existence apart from a thinking mind is not conceivable.

The foregoing reasoning will be in no way affected, if, instead of pricking the finger, the point of the pin rests gently against it, so as to give rise merely to a tactile sensation. The tactile sensation is referred outwards to the point touched, and seems to exist there. But it is certain that it is not and cannot be there really, because the brain is the sole seat of consciousness; and, further, because evidence, as strong as that in favour of the sensation being in the finger, can be brought forward in support of propositions which are manifestly absurd.

For example, the hairs and nails are utterly devoid of sensibility, as everyone knows. Nevertheless, if the ends of the nails or hairs are touched, ever so lightly, we feel that they are touched, and the sensation seems to be situated in the nails or hairs. Nay more, if a walking-stick a yard long is held firmly by the handle and the other end is touched, the tactile sensation, which is a state of our own consciousness, is unhesitatingly referred to the end of the stick; and yet no one will say that it _is_ there.

Let us now suppose that, instead of one pin's point resting against the end of my finger, there are two. Each of these can be known to me, as we have seen, only as a state of a thinking mind, referred outwards, or localized. But the existence of these two states, somehow or other, generates in my mind a host of new ideas, which did not make their appearance when only one state was present.

For example, I get the ideas of co-existence, of number, of distance, and of relative place or direction. But all these ideas are ideas of relations, and imply the existence of something which perceives those relations. If a tactile sensation is a state of the mind, and if the localization of that sensation is an act of the mind, how is it conceivable that a relation between two localized sensations should exist apart from the mind? It is, I confess, quite as easy for me to imagine that redness may exist apart from a visual sense, as it is to suppose that co-existence, number, and distance can have any existence apart from the mind of which they are ideas.

Thus it seems clear that the existence of some, at any rate, of Locke's primary qualities of matter, such as number and extension, apart from mind, is as utterly unthinkable as the existence of colour and sound under like circumstances.

Will the others--namely, figure, motion and rest, and solidity--withstand a similar criticism? I think not. For all these, like the foregoing, are perceptions by the mind of the relations of two or more sensations to one another. If distance and place are inconceivable, in the absence of the mind, of which they are ideas, the independent existence of figure, which is the limitation of distance, and of motion, which is change of place, must be equally inconceivable. Solidity requires more particular consideration, as it is a term applied to two very different things, the one of which is solidity of form, or geometrical solidity; while the other is solidity of substance, or mechanical solidity.

If those motor nerves of a man by which volitions are converted into motion were all paralysed, and if sensation remained only in the palm of his hand (which is a conceivable case), he would still be able to attain to clear notions of extension, figure, number, and motion, by attending to the states of consciousness which might be aroused by the contact of bodies with the sensory surface of the palm. But it does not appear that such a person could arrive at any conception of geometrical solidity. For that which does not come in contact with the sensory surface is non-existent for the sense of touch; and a solid body, impressed upon the palm of the hand, gives rise only to the notion of the extension of that particular part of the solid which is in contact with the skin.

Nor is it possible that the idea of outness (in the sense of discontinuity with the sentient body) could be attained by such a person; for, as we have seen, every tactile sensation is referred to a point either of the natural sensory surface itself, or of some solid in continuity with that surface. Hence it would appear that the conception of the difference between the Ego and the non-Ego could not be attained by a man thus situated. His feelings would be his universe, and his tactile sensations his "moenia mundi." Time would exist for him as for us, but space would have only two dimensions.

But now remove the paralysis from the motor apparatus, and give the palm of the hand of our imaginary man perfect freedom to move, so as to be able to glide in all directions over the bodies with which it is in contact. Then with the consciousness of that mobility, the notion of space of three dimensions--which is "_Raum_" or "room" to move with perfect freedom--is at once given. But the notion that the tactile surface itself moves, cannot be given by touch alone, which is competent to testify only to the fact of change of place, not to its cause. The idea of the motion of the tactile surface could not, in fact, be attained, unless the idea of change of place were accompanied by some state of consciousness, which does not exist when the tactile surface is immoveable. This state of consciousness is what is termed the muscular sense, and its existence is very easily demonstrable.

Suppose the back of my hand to rest upon a table, and a sovereign to rest upon the upturned palm, I at once acquire a notion of extension, and of the limit of that extension. The impression made by the circular piece of gold is quite different from that which would be made by a triangular, or a square, piece of the same size, and thereby I arrive at the notion of figure. Moreover, if the sovereign slides over the palm, I acquire a distinct conception of change of place or motion, and of the direction of that motion. For as the sovereign slides, it affects new nerve-endings, and gives rise to new states of consciousness. Each of them is definitely and separately localized by a reflex act of the mind, which, at the same time, becomes aware of the difference between two successive localizations; and therefore of change of place, which is motion.

If, while the sovereign lies on the hand, the latter being kept quite steady, the fore-arm is gradually and slowly raised; the tactile sensations, with all their accompaniments, remain exactly as they were. But, at the same time, something new is introduced; namely, the sense of effort. If I try to discover where this sense of effort seems to be, I find myself somewhat perplexed at first; but, if I hold the fore-arm in position long enough, I become aware of an obscure sense of fatigue, which is apparently seated either in the muscles of the arm, or in the integument directly over them. The fatigue seems to be related to the sense of effort, in much the same way as the pain which supervenes upon the original sense of contact, when a pin is slowly pressed against the skin, is related to touch.

A little attention will show that this sense of effort accompanies every muscular contraction by which the limbs, or other parts of the body, are moved. By its agency the fact of their movement is known; while the direction of the motion is given by the accompanying tactile sensations. And, in consequence of the incessant association of the muscular and the tactile sensations, they become so fused together that they are often confounded tinder the same name.

If freedom to move in all directions is the very essence of that conception of space of three dimensions which we obtain by the sense of touch; and if that freedom to move is really another name for the feeling of unopposed effort, accompanied by that of change of place, it is surely impossible to conceive of such space as having existence apart from that which is conscious of effort.

But it may be said that we derive our conception of space of three dimensions not only from touch, but from vision; that if we do not feel things actually outside us, at any rate we see them. And it was exactly this difficulty which presented itself to Berkeley at the outset of his speculations. He met it, with characteristic boldness, by denying that we do see things outside us; and, with no less characteristic ingenuity, by devising that "New Theory of Vision" which has met with wider acceptance than any of his views, though it has been the subject of continual controversies.[1]

[Footnote 1: I have not specifically alluded to the writings of Bailey, Mill, Abbott, and others, on this vexed question, not because I have failed to study them carefully, but because this is not a convenient occasion for controversial discussion. Those who are acquainted with the subject, however, will observe that the view I have taken agrees substantially with that of Mr. Barley.]

In the "Principles of Human Knowledge," Berkeley himself tells us how he was led to those views which he published in the "Essay towards the New Theory of Vision."

"It will be objected that we see things actually without, or
at a distance from us, and which consequently do not exist in
the mind; it being absurd that those things which are seen at
the distance of several miles, should be as near to us as our
own thoughts. In answer to this, I desire it may be considered
that in a dream we do oft perceive things as existing at a
great distance off, and yet, for all that, those things are
acknowledged to have their existence only in the mind.

"But for the fuller clearing of this point, it may be worth
while to consider how it is that we perceive distance and
things placed at a distance by sight. For that we should in
truth see external space and bodies actually existing in it,
some nearer, others further off, seems to carry with it some
opposition to what hath been said of their existing nowhere
without the mind. The consideration of this difficulty it
was that gave birth to my 'Essay towards the New Theory of
Vision,' which was published not long since, wherein it is
shown that distance, or outness, is neither immediately of
itself perceived by sight, nor yet apprehended, or judged
of, by lines and angles or anything that hath any necessary
connection with it; but that it is only suggested to our
thoughts by certain visible ideas and sensations attending
vision, which, in their own nature, have no manner of
similitude or relation either with distance, or with things
placed at a distance; but by a connection taught us by
experience, they come to signify and suggest them to us, after
the same manner that words of any language suggest the ideas
they are made to stand for; insomuch that a man born blind and
afterwards made to see, would not, at first sight, think the
things he saw to be without his mind or at any distance from
him."

The key-note of the Essay to which Berkeley refers in this passage is to be found in an italicized paragraph of section 127:--

"_The extensions; figures, and motions perceived by sight are
specifically distinct from the ideas of touch called by the
same names; nor is there any such thing as an idea, or kind of
idea, common to both senses_."

It will be observed that this proposition expressly declares that extension, figure, and motion, and consequently distance, are immediately perceived by sight as well as by touch; but that visual distance, extension, figure, and motion, are totally different in quality from the ideas of the same name obtained through the sense of touch. And other passages leave no doubt that such was Berkeley's meaning. Thus in the 112th section of the same Essay, he carefully defines the two kinds of distance, one visual, the other tangible:--

"By the distance between any two points nothing more is meant
than the number of intermediate points. If the given points
are visible, the distance between them is marked out by the
number of interjacent visible points; if they are tangible,
the distance between, them is a line consisting of tangible
points."

Again, there are two sorts of magnitude or extension:--

"It has been shown that there are two sorts of objects
apprehended by sight, each whereof has its distinct magnitude
or extension: the one properly tangible, _i.e._ to be
perceived and measured by touch, and not immediately falling
under the sense of seeing; the other properly and immediately
visible, by mediation of which the former is brought into
view."--§ 55.

But how are we to reconcile these passages with others which will be perfectly familiar to every reader of the "New Theory of Vision "? As, for example:--

"It is, I think, agreed by all, that distance of itself, and
immediately, cannot be seen."--§ 2.

"Space or distance, we have shown, is no otherwise the object
of sight than of hearing."--§ 130.

"Distance is in its own nature imperceptible, and yet it is
perceived by sight. It remains, therefore, that it is
brought into view by means of some other idea, that is itself
immediately perceived in the act of vision."--§ 11.

"Distance or external space."--§ 155.

The explanation is quite simple, and lies in the fact that Berkeley uses the word "distance" in three senses. Sometimes he employs it to denote visible distance, and then he restricts it to distance in two dimensions, or simple extension. Sometimes he means tangible distance in two dimensions; but most commonly he intends to signify tangible distance in the third dimension. And it is in this sense that he employs "distance" as the equivalent of "space." Distance in two dimensions is, for Berkeley, not space, but extension. By taking a pencil and interpolating the words "visible" and "tangible" before "distance" wherever the context renders them necessary, Berkeley's statements may be made perfectly consistent; though he has not always extricated himself from the entanglement caused by his own loose phraseology, which rises to a climax in the last ten sections of the "Theory of Vision," in which he endeavours to prove that a pure intelligence able to see, but devoid of the sense of touch, could have no idea of a plane figure. Thus he says in section 156:--

"All that is properly perceived by the visual faculty amounts
to no more than colours with their variations and different
proportions of light and shade; but the perpetual mutability
and fleetingness of those immediate objects of sight
render them incapable of being managed after the manner of
geometrical figures, nor is it in any degree useful that they
should. It is true there be divers of them perceived at once,
and more of some and less of others; but accurately to compute
their magnitude, and assign precise determinate proportions
between things so variable and inconstant, if we suppose
it possible to be done, must yet be a very trifling and
insignificant labour."

If, by this, Berkeley means that by vision alone, a straight line cannot be distinguished from a curved one, a circle from a square, a long line from a short one, a large angle from a small one, his position is surely absurd in itself and contradictory to his own previously cited admissions; if he only means, on the other hand, that his pure spirit could not get very far on in his geometry, it may be true or not; but it is in contradiction with his previous assertion, that such a pure spirit could never attain to know as much as the first elements of plane geometry.

Another source of confusion, which arises out of Berkeley's insufficient exactness in the use of language, is to be found in what he says about solidity, in discussing Molyneux's problem, whether a man born blind and having learned to distinguish between a cube and a sphere, could, on receiving his sight, tell the one from the other by vision. Berkeley agrees with Locke that he could not, and adds the following reflection:--

"Cube, sphere, table, are words he has known applied to things
perceivable by touch, but to things perfectly intangible
he never knew them applied. Those words in their wonted
application always marked out to his mind bodies or solid
things which were perceived by the resistance they gave. But
there is no solidity, no resistance or protrusion perceived by
sight."

Here "solidity" means resistance to pressure, which is apprehended by the muscular sense; but when in section 154 Berkeley says of his pure intelligence--

"It is certain that the aforesaid intelligence could have no
idea of a solid or quantity of three dimensions, which follows
from its not having any idea of distance "--

he refers to that notion of solidity which may be obtained by the tactile sense, without the addition of any notion of resistance in the solid object; as, for example, when the finger passes lightly over the surface of a billiard ball.

Yet another source of difficulty in clearly understanding Berkeley arises out of his use of the word "outness." In speaking of touch he seems to employ it indifferently, both for the localization of a tactile sensation in the sensory surface, which we really obtain through touch; and for the notion of corporeal separation, which is attained by the association of muscular and tactile sensations. In speaking of sight, on the other hand, Berkeley employs "outness" to denote corporeal separation.

When due allowance is made for the occasional looseness and ambiguity of Berkeley's terminology, and the accessories are weeded out of the essential parts of his famous Essay, his views may, I believe, be fairly and accurately summed up in the following propositions:--

1. The sense of touch gives rise to ideas of extension, figure, magnitude, and motion.

2. The sense of touch gives rise to the idea of "outness," in the sense of localization.

3. The sense of touch gives rise to the idea of resistance, and thence to that of solidity, in the sense of impenetrability.

4. The sense of touch gives rise to the idea of "outness," in the sense of distance in the third dimension, and thence to that of space, or geometrical solidity.

5. The sense of sight gives rise to ideas of extension, of figure, magnitude, and motion.

6. The sense of sight does not give rise to the idea of "outness," in the sense of distance in the third dimension, nor to that of geometrical solidity, no visual idea appearing to be without the mind, or at any distance off (§§ 43, 50).

7. The sense of sight does not give rise to the idea of mechanical solidity.

8. There is no likeness whatever between the tactile ideas called extension, figure, magnitude, and motion, and the visual ideas which go by the same names; nor are any ideas common to the two senses.

9. When we think we see objects at a distance, what really happens is that the visual picture suggests that the object seen has tangible distance; we confound the strong belief in the tangible distance of the object with actual sight of its distance.

10. Visual ideas, therefore, constitute a kind of language, by which we are informed of the tactile ideas which will, or may, arise in us.

Taking these propositions into consideration _seriatim_, it may be assumed that everyone will assent to the first and second; and that for the third and fourth we have only to include the muscular sense tinder the name of sense of touch, as Berkeley did, in order to make it quite accurate. Nor is it intelligible to me that anyone should explicitly deny the truth of the fifth proposition, though some of Berkeley's supporters, less careful than himself, have done so. Indeed, it must be confessed that it is only grudgingly, and as it were against his will, that Berkeley admits that we obtain ideas of extension, figure, and magnitude by pure vision, and that he more than half retracts the admission; while he absolutely denies that sight gives us any notion of outness in either sense of the word, and even declares that "no proper visual idea appears to be without the mind, or at any distance off." By "proper visual ideas," Berkeley denotes colours, and light, and shade; and, therefore, he affirms that colours do not appear to be at any distance from us. I confess that this assertion appears to me to be utterly unaccountable. I have made endless experiments on this point, and by no effort of the imagination can I persuade myself, when looking at a colour, that the colour is in my mind, and not at a "distance off," though of course I know perfectly well, as a matter of reason, that colour is subjective. It is like looking at the sun setting, and trying to persuade oneself that the earth appears to move and not the sun, a feat I have never been able to accomplish. Even when the eyes are shut, the darkness of which one is conscious, carries with it the notion of outness. One looks, so to speak, into a dark space. Common language expresses the common experience of mankind in this matter. A man will say that a smell is in his nose, a taste in his mouth, a singing in his ears, a creeping or a warmth in his skin; but if he is jaundiced, he does not say that he has yellow in his eyes, but that everything looks yellow; and if he is troubled with _muscae volitantes_, he says, not that he has specks in his eyes, but that he sees specks dancing before his eyes. In fact, it appears to me that it is the special peculiarity of visual sensations, that they invariably give rise to the idea of remoteness, and that Berkeley's dictum ought to be reversed. For I think that anyone who interrogates his consciousness carefully will find that "every proper visual idea" appears to be without the mind and at a distance off.