Th. [But then many philosophers would not ascribe hard ness to their atoms. The notion of hardness does not depend upon the senses, and its possibility can be conceived by the reason, although we are further convinced by the senses that it is actually found in nature. I should, however, prefer the word compactness — fermete (if I were allowed to use the word in this sense) — to that of hardness, for there is some compact ness even in soft bodies. I seek even a more suitable and general term, like consistence or cohesion. Thus I would oppose hard to soft, solid to fluid, for wax is soft, but, iinless melted by heat, it is not fluid and preserves its bounds; and in fluids even there is ordinarily cohesion, as is shown in drops of water and of mercury. I am also of opinion that all bodies have some degree of cohesion., as I also believe that there are none which do not have some fluidity, and whose cohesion is not capable of being overcome; so that, in my opinion, the atoms of Epicurus,1 whose hardness is supposed to be invinci ble, cannot occur any more than the subtile, perfectly fluid matter of the Cartesians. But this is not the place to justify this opinion or to explain the rationale of cohesion.
Ph. The perfect solidity of bodies seems to be justified by experiment. For example, water incapable of yielding, passed through the pores of a hollow globe of gold, in which it was confined, when this globe was put under pressure in Florence.
Th. [There is something to be said as to the inference which you draw from this experiment, and from what happened in the case of the water. The air as well as the water is a body, which is compressible at least ad sensum, and those who would maintain a complete rarefaction and condensation will say that water is already too compressed to yield to our machines, as air very much compressed would resist also a further compres sion. I admit, however, on the other hand, that if any slight change should be noticed in the volume of the water, it might be ascribed to the air which is enclosed in it. Without enter- 1 Epicurus, December, 342, or January, 341-270 B.C. — TB.
CH. iv] ON HUMAN UNDERSTANDING 127 ing now into the discussion whether pure water is not itself compressible, as it is found that it is dilatable when it evapo rates, I am, nevertheless, decidedly of the opinion of those who believe that bodies are perfectly impenetrable, and that there is, save in appearance, neither condensation nor rarefaction. But this kind of experiment is as little capable of proving this as the tube of Torricelli * or the machine of Guerike 2 are suffi cient to prove a perfect vacuum.3 § 5. Ph. If the body were strictly capable of rarefaction and compression, it might change in volume or extension, but that not being so, it will be always equal to the same space; and, moreover, its extension will be always distinct from that of space.
Th. [The body might have its own extension, but it does not thereby follow that it would be always determinate or equal to the same space. Nevertheless, although it may be true that in the conception of body something besides space is conceived of, it does not thereby follow that there are two extensions — that of space and that of body; for it is as when in conceiving several things at once, one conceives something besides the number, viz.: res numerates,; and, moreover, there are not two multitudes, the one abstract — i.e., that of number; the other concrete — i.e., that of the things enumerated. Likewise one can say that it is not necessary to think of two extensions — the one abstract, of space, the other concrete, of body, the con- 1 Evangelista Torricelli, 1608-1647, a celebrated Italian physicist and mathe matician, the inventor of the mercurial barometer, long called the " Torricel lian tube." He had a controversy with Roberval (vid. ante, p. 107 and note) as to the discovery of the quadrature of the cycloid. Torricelli found the area of the curve, and furnished the demonstration of it, which he published in a tract, l)e motu gravium naturaliter accelerato in his Opera geometrica, Florence, 2 Otto von Guerike, 1002-1686, a German physicist, who devoted himself especially to experimenting upon the vacuum, and who, after many attempts, finally, in 1654, hit upon an air machine, which enabled him to undertake a series of experiments upon the different effects of vacuum. His labors and principal observations have been published under the title, Experimentanova, ut vacant, Magdeburgica, de vacuo spatio, etc., Amsterdam, 1672. — TR.
3 Descartes maintained the impossibility of a vacuum. Cf. Prin. Philos., II., § 16; English translation by John Veitch, LL.D., The Method, Meditations, and Selections from the Principles of Descartes, etc., 8th ed., p. 241, Edin burgh: William Blackwood & Sons, 1881; also vid. ante, p. 16, and the fifth letter to Samuel Clarke, §.'34, Gerhardt, Vol. 7, p..'W5; Erdmann, p. 766, b; translation, Duncan, Philos. Works of Leibnitz, p. 262. — TR.
128 LEIBNITZ'S CRITIQUE OF LOCKE [UK. n Crete existing as such only through the abstract. And as bodies pass from one part of space to another — i.e., change order among themselves — things also pass from one part of the order or of a number to the other, when, for example, the first becomes the second and the second the third, etc. In fact, time and space are only kinds of order,1 and in these orders the vacant place (which in relation to space is called vacuum), if there were any, would show the possibility only of that which is lacking together with its relation to the actual.
Ph. I am nevertheless very glad that you agree with me that matter does not change in volume. But you seem to go too far, sir, in not recognizing two extensions, and you re- seinble the Cartesians, who do not distinguish space from mat ter.2 Now it seems to me that if a class is found who, not having these distinct ideas (of space and of solidity which fills it), blends them and makes of the two one only, we cannot see how these persons can converse with others. They are like a blind man who, when another man speaks to him of scarlet, thinks it resembles the sound of a trumpet.
Th. [But I hold at the same time that the ideas of exten sion and solidity, like that of scarlet-color, do not consist in an / know not tvhat.3 I distinguish extension and matter, contrary 1 Cf. Letter to Des Bosses, June 16, 1712, Gerhardt, Vol. 2, p. 450; Erdmann, p. 682, b: " Spatiura fit ordo coexistentium phsenomenorum, ut tempus sueces- sivoruin," i.e. " Space is the order of co-existing, as time of successive phe nomena "; also the letters to Clarke, Gerhardt, Vol. 7, pp. 345 sq.; Erdmann, pp. 746s?., translation, Duncan, Philos. Works of Leibnitz, pp. 238 sq.; Kant, Kritik d. r. Vernunft, Erst. Th., Ahsch. 1 und 2, §§ 2-7, and translations of Max Miiller, and Watson in The Philosophy of Kant, as contained in extracts from his own writings. New York: Macmillan & Co., 1888. — TR.
2 Cf. Descartes, Prin. Philos. II., §§ 8-15; Veitch's translation, pp. 236-240.
8 Leibnitz's expression is "un je ne say qwoi." Schaarschmidt trans lates it " ein undenkbares Etwax." It seems to be equivalent to an indef inite somewhat which is the ultimate essence of things, and which is the cause of, and by differentiation becomes, the particular. Leibnitz, then, means to say that the ideas of extension and solidity are distinct. Cf. John Dewey, Pli.D., Leibniz's New Essays concerning the Human Understanding, a Critical Exposition, p. 134. As applied to personal beings, it seems to be equivalent to the "unconscious presentations" — i.e. "the dark side of the soul-life," " the proper basis of Individuality." " Genius, disposition, feeling, are the terms by which a later time has designated what Leibnitz calls the je ne sais quoi, whereby every one is preformed by nature to something par ticular" ("Ganz wie bei clem blossen Monaden ihre individuelle Beschaffeu- heit in dcm Momente der Schranke, der materia prima, lag, ganz so werden CH. v] ON HUMAN UNDERSTANDING 129 to the view of the Cartesians. Still I do not believe that there are two extensions; and since those who dispute over the dif ference between extension and solidity are agreed on several truths upon this subject and have some distinct notions, they can find therein the means of extricating themselves from their disagreement; thus the assumed difference upon ideas ought not to serve as a pretext for eternal disputes, although I know that certain Cartesians, otherwise very able, are accustomed to intrench themselves in the ideas which they pretend to have. But if they would avail themselves of the means which I have before given for recognizing ideas true and false, and of which we shall speak also in the sequel, they would retire from a position which is not tenable.
CHAPTER V OF SIMPLE IDEAS WHICH COME BY DIFFERENT SENSES Ph. The ideas, the perception of which comes to us from more than one sense, are those of space, or extension, or fig ure, of motion and rest.
Th. [The ideas which are said to come from more than one sense, like those of space, figure, motion, rest, are rather from common-sense, that is to say, from the mind itself, for they are ideas of the pure understanding, but related to externality, and which the senses make us perceive; they are also capable of definition and demonstration.]
hier diese unbewussten Vorstellungen, d. h. wird die dunkle Seite des Seelen- lebens, als der eigentliche Grund der Individualitat bestimmt. Genius, Gemiith, Gefiihl sind die Worte, rait denen eine spatere Zeit das bezeichnet bat, was Leibnitz das je ne sais quoi nennt, wodurch Jeder von Natur zu etwas Besonderem praformirt ist." Erdmann, Grundriss d. Gesch. d. Philos., 3te Autiage 2te Bd. § 288, 5, s. 161. Berlin, 1878; English translation, Vol. 2, p. 191, London: Swan Sonnenscbein & Co., 1889). Cf. also Leibnitz, New Essays, Preface, vid. ante, pp. 47 sq., Book II., chap. 1, § 15, Th., sq., and Erdmann's exposition of the same, op. cit., s. 160, 161. Also Professor Dewey's most excellent work cited above. — TB.
K K 130 LEIBNITZ'S CRITIQUE OF LOCKE [BK. n CHAPTER VI OF SIMPLE IDEAS WHICH COME BY REFLECTION Ph. The simple ideas which come by reflection are the ideas of the understanding and of the will [for we ourselves per ceive them in reflecting upon ourselves.]
Tli. [It is doubtful if all these ideas are simple, for it is clear, for example, that the idea of the will includes that of the understanding, and that the idea of motion contains that of figure.
CHAPTER VII OF IDEAS WHICH COME BY SENSATION AND REFLECTION § 1. Ph. There are some simple ideas which make themselves perceived in the mind by all the avenues of sensation and by reflection also — viz.: pleasure, pain, power, existence, unity.
Th. [It seems that the senses cannot convince us of the exist ence of sensible things without the aid of the reason. Thus I should think that the idea1 of existence comes from reflection. That of power also and of unity come from the same source, and are of a wholly different nature from the perceptions of pleasure and pain.]
CHAPTER VIII OTHER CONSIDERATIONS UPON SIMPLE IDEAS § 2. Ph. What shall we say of ideas of privative qualities? It seems to me that the ideas of rest, darkness, and cold are as positive as those of motion, light, and heat. Nevertheless, in proposing these privations as the causes of privative ideas I follow the common view; but in the main it will be difficult 1 The French is "la consideration de 1' existence." — TR.
CH. VIH] ON HUMAN UNDERSTANDING 131 to determine whether there is really any idea which arises from a privative cause until it has been determined whether rest any more than motion is a privation.
Th. [I had not believed that we could have reason to doubt the privative nature of rest. It suffices it that motion in the body be denied, but it does not suffice for motion to deny rest, and it is necessary to add something more to determine the de gree of motion, since it receives materially more or less, while all rest is equal. It is another thing when we speak of the cause of rest, which must be positive in the secondary1 matter or mass. I should furthermore regard the very idea of rest as privative — i.e., that it consists only in negation. It is true that the act of denial is positive.]
§ 9. Ph. The qualities of things being the faculties they have of producing in us perception of ideas, it is well to distinguish these qualities. They are primary and secondary. Extension, solidity, figure, number, mobility are the original qualities inseparable from body which I call primary. § 10. But I call 1 Leibnitz constantly distinguishes between primary and secondary matter. Primary matter is the primitive passive power belonging to each separate being as such, by which it is distinguished from God and in which is grounded the possibility of representing itself as different. It is essential to and insepa rable from the entelechy, or principle of activity, which it completes, the two united producing the perfect substance or monad. By itself it is a pure abstraction or potentiality, and not a substance. It is equivalent to confused ideas, thus to an imperfect manifestation or phenomenon of spirit — since all matter is ultimately spirit or has its final reason or source in spirit — but a potentiality of spirit capable sometime of realizing perfectly all its intrinsic, but now latent, activity. Secondary matter is a mass resulting from the union of many monads or complete substances, each having its own primary matter and its own entelechy, with their derived forces, activities, receptivities. It is not, however, a substance; and its extension resulting from the union of non-extended simple substances is only phenomenal, though not on that account unreal, being due to our confused perception, and consisting in the impenetrability, resistance, or inertia of the monad on its passive side; an extension which will disappear when the activity of the monad becomes pure and perfect. Cf. Letters to Tolomei, Dec. 17, 1705, Gerhardt, Vol. 7, pp. 467- 468; Des Bosses, March 11, Oct. 16, 1706, March 16, 1700, Gerhardt, Vol. 2, pp. 304, 324, 368; Erdmann, pp. 435, 440, 456; De anima brutonnn, 1710, G. 7, 328; E. 463; Letters to Rud. Christ. Wagner, June 4, 1710, G. 7, 528, E. 465; translation, Duncan, Philos. Works of Leibnitz, p. 190 sq.; Bierling, Aug. 12, 1711, G. 7, 500-502, E. 677-678; Remo'nd, Nov. 4, 1715, G. 3, 656-660; E. 735- 737; Feb. 11, 1715, § 4 (reply to Remond's fourth difficulty stated in his letter to Leibnitz, Jan. 9, 1715), G. 3, 636, E. 725; also the writing dated July, 1714, and first published by Gerhardt, 3,622-624. Cf. also Erdmann, Grundl d. Gesch.d. Philos., 3d ed., §*288, 2, 3; Dewey, Leibnitz, New Essays, chaps. 7 and 8. — TR.
132 LEIBNITZ'S CRITIQUE OF LOCKE [BK. H secondary qualities the faculties or powers of bodies to produce certain sensations in us, or certain effects in other bodies, as the fire, for example, produces a certain effect in the wax when melting it.
Th. [I think we can say that when the power is intelligible, and can be distinctly explained, it should be reckoned among the primary qualities; but when it is only sensible and gives only a confused idea, it should be put among the secondary qual ities.']
§ 11. Ph. These primary qualities show how bodies act upon one another. Now, bodies act only by impulse, at least so far as we can conceive the process, for it is impossible to under stand how bodies can act upon what they do not touch, which is equivalent to imagining that they can act where they are not.
Th. [I am also of the opinion that bodies act only by impulse. Yet, there is some difficulty in the proof of what I have just heard; for attraction sometimes occurs without contact, and we can touch and draw without any visible impulse, as I have shown above * in speaking of hardness. In the case of the atoms of Epicurus, the one part pushed would draw the other with it, and would touch it in putting it in motion without impulse. And in the case of attraction between contiguous things we cannot say that the one which draws with itself acts where it is not. This reason would militate only against attractions from a distance, as would be the case in reference to Avhat are called vires centripetce advanced by some scholars.]
§ 13. Ph. Now, certain particles, striking our organs in a cer tain way, cause in us certain sensations of colors or tastes or other secondary qualities which have the power of producing these sensations. And it is no more difficult to conceive that God can attach such ideas (as that of heat) to motions, with which they have no resemblance, than it is difficult to conceive that he has attached the idea of pain to the motion of a piece of iron which divides our flesh; which motion the pain in no manner resembles.
Th. [It is not necessary to suppose that ideas like those of color or of pain are arbitrary and without relation or natural connection with their causes; it is not the custom of God to * Cf. Bk. II., Chap. 4, § 4, Th., ante, p. 125, sq. — TK.
CH. vin] ON HUMAN UNDERSTANDING 133 act with so little order and reason. I should rather say that there is a kind of resemblance, not complete and, so to speak, in terminis, but expressive, or a kind of orderly relation, as an ellipse, and even a parabola or hyperbola resemble in some sense the circle of which they are a projection upon a plane, since there is a certain exact and natural relation between what is projected and the projection which is made, each point of the one corresponding by a certain relation to each point of the other. This the Cartesians do not sufficiently consider, and for once you have deferred to them more than has been customary with you, and without reason for so doing.]
§ 15. Ph. I tell you what appears to me, and the appear ances are that the ideas of the primary qualities of bodies resemble these qualities, but the ideas produced in us by the secondary qualities resemble them in no way.
Th. [I have just shown how there is resemblance or exact relation in respect to the secondary as well as the primary qualities. It is certainly reasonable that the effect correspond to its cause; and how assert the contrary, since you know dis tinctly neither the sensation of blue (for example) nor the motions which produce it? It is true that pain does not resemble the motion of a pin, but it may very well resemble the motions which this pin causes in our body, and represent these motions in the soul, as I have no doubt it does. It is also for this reason that we say that the pain is in our body and not that it is in the pin; but we say that the light is in the fire, because there are in the fire motions which are not dis tinctly sensible apart from it, but whose confusion or con junction becomes sensible, and is represented to us by the idea of light.
§ 21. Ph. But if the relation between the object and the sensation be natural, how can it be, as we notice in fact, that the same water may appear warm to one hand and cold to the other? which shows that the heat is no more in the water than the pain is in the pin.
Th. [This proves all the more that heat is not a sensible quality or power of making itself felt absolutely all at once, but that it is relative to the suitable organs; for a particular motion in the hand may be mixed with it and change its appear ance. Light, furthermore, does not make itself evident to 134 LEIBNITZ'S CRITIQUE OF LOCKE [BK. n badly constituted eyes, and when they are themselves filled with a great light, they are insensible to a less. Even the primary qualities (according to our classification) — for ex ample, unity and number — may not appear as they should; for, as Descartes has already stated, a globe touched by the fingers in a certain way appears double, and mirrors or glasses cut in facets multiply the object. It does not then follow that what does not always appear the same is not a quality of the object, and that its image does not resemble it. And as for the heat, when our hand is very warm, the medium heat of the water does not make itself felt, and modifies rather that of the hand, and consequently the water appears to us cold; as the salt water of the Baltic Sea mixed with the water of the Sea of Portugal1 would lessen its specific saline quality, although the former be itself salt. Thus, in any case, we can say that the heat belongs to the water of a bath, although it may appear cold to any one, as honey is- called absolutely sweet, and silver white, although the one appears bitter, the other yellow to some diseased persons, for the classification is made upon the basis of the most common (conditions); and yet it remains true that, when the organ and the medium are constituted as they should be, the internal motions and the ideas which represent them to the soul resemble the motions of the object which cause color, heat, pain, etc., or, what is here the same thing, express it by means of a relation suffi ciently exact, although this relation does not distinctly appear to us, because we cannot disentangle this multitude of small impressions either in our soul or our body or in what is with out.
§ 24. Ph. We consider the qualities which the sun has of blanching or melting wax or hardening mud only as simple powers, without thinking of anything in the sun correspond ing to this blanching, softness, or hardness; but heat and light are commonly regarded as real qualities of the sun. Properly considered, however, these qualities of light and heat which in me are perceptions are not in the sun in any other manner than the changes produced in the wax when it is blanched or melted.
1 Obsolete name for that part of the Atlantic which washes the coast of Portugal. — TR.
en. ix] ON HUMAN UNDERSTANDING 135 Th. [Some have pushed this doctrine so far that they have desired to persuade us that if any one could touch the sun he would find there no heat. The counterfeit sun which makes itself felt in the focus of a mirror or a burning-glass may disa buse people of this notion. But as to the comparison between the power of heating and that of melting, I dare affirm that if the melted or blanched wax had feeling, it would feel some thing similar to what we feel when the sun warms us, and would say, if it could, that the sun is warm, not because its whiteness resembles the sun — for when faces are tanned in the sun their brown color should likewise resemble it — but because there are in the wax motions which are related to those in the sun which cause them; its whiteness may come from another cause, but not the motions which it has had in receiving it (whiteness) from the sun.]
CHAPTER IX OF PERCEPTION § 1. Ph. Come we now to the ideas of reflection in particu lar. Perception is the first faculty of the soul which is occu pied with our ideas. It is also the first and simplest idea which we receive by reflection. Thought signifies often the mind's working upon its own ideas, when it acts and considers a thing with a certain degree of voluntary attention: but in what we call perception the mind is ordinarily purely passive, not being able to avoid perceiving what it actually perceives.
Th. [We might perhaps add that the animals have percep tion, and that it is not necessary that they have thought, that is to say, that they have reflection or what may be its object. We ourselves also have minute perceptions of which we are not conscious in our present state. It is true that we might very well perceive them ourselves, and reflect upon them, if we were not turned aside by their multitude, which distracts our mind, or if they were not effaced, or rather obscured, by greater ones.
§ 4. Ph. I admit that when the mind is strongly occupied 136 LEIBNITZ'S CRITIQUE OF LOCKE [UK. n in contemplating certain objects it does not perceive in any way the impression which certain bodies make upon the organ of hearing, although the impression may be quite strong; but no perception arises therefrom if the soul takes no cognizance thereof.
Th. [I should prefer to distinguish between perception and consciousness (swapper cevoir).1 The perception of light and color, for example, of which we are conscious, is composed of many minute perceptions, of which we are not conscious; and a noise which we perceive, but of which we take no notice, becomes apperceptible by a little addition or increase; for if what precedes make no impression upon the soul, this little addition would also make none, and the whole would make no more. I have already touched upon this point (Ch. II,2 of § 8. Ph. It is proper to remark here that the ideas which arise from sensation are often altered by the mental judgment of grown persons without their perceiving the fact. A flat circle with various light and shade represents the idea of a globe of uniform color. But, as we are accustomed to distin guish the images of bodies and the changes of the reflections of light according to the figures of their surfaces, we put in the place of what appears to us the cause the image itself, and confuse the judgment with the appearance.
Th. Nothing is truer, and this it is which gives to painting the means of deceiving us by the artifice of a very extended perspective. When bodies have flat surfaces, they can be rep resented without employing shadows by giving only their con tours and by simply making pictures after the fashion of the Chinese, but better proportioned than theirs. The same 1 Cf. Leibnitz, Principes de la nature et de la grace fonde~s en raison, § 4. " It is well to make a distinction between the perception, which is the internal condition of the monad representing external things, and apperception, which is consciousness or the reflective knowledge of this internal state: the latter not being given to all sonls, nor at all times to the same sonl." For the entire piece, which is a brief statement of his philosophical system prepared by Leibnitz; himself, with the greatest care, about 1714, cf. Gerhardt, Vol. 6, pp. 598-fiOO; Erdmann, pp. 714-718; translation, Duncan, Philos. Works of Leibnitz, pp. 209-217, and note Ofi, p.,387 op. cit. Also Hamilton's Reid, 8th ed., Vol. 2, p. 877, note, and Krautb-Fleming, Vocab. Philos., ed. of 1877, articles "Apperception," p. 38, " Consciousness," pp. 100-113,613, "Percep tion," pp. 373-374, 807-809, "Perceptions (Obscure)," pp. 374-376. — TR.
2 This should be chap. 1, I think.— TR.
en. ixj ON HUMAN UNDERSTANDING 137 custom is observed in designing medals, in order that the draughtsman may be less likely to depart from the precise form of the antique. But we cannot distinguish exactly by means of the design the interior of a circle from the interior of a spherical surface bounded by this circle without the aid of shadows, the interior of each having neither points distin guished nor distinguishing features, although there is, however, a great difference which ought to be indicated. Desargues l has accordingly given precepts upon the force of tints and shades. When, then, a painting deceives us there is a double error in our judgments; for first we put the cause for the effect, and think we see immediately the cause of the image, in which we resemble a little a dog who barks at a mirror; for, properly speaking, we see only the image, and we are affected only by the rays of light. And since the rays of light require time (how ever little it be), it is possible for the object to be destroyed in this interval, and for it no longer to exist when the ray reaches the eye, and that which no longer exists cannot be the object present to the sight. In the second place, we further deceive ourselves when we put one cause for another, and think that