But in consequence of that unduly wide view in abstract thought of the conception cause, which was considered above, it has been confounded with the conception of force. This is something completely different from the cause, but yet is that which imparts to every cause its causality, i.e., the capability of producing an effect. I have explained this fully and thoroughly in the second book of the first volume, also in “The Will in Nature,” and finally also in the second edition of the essay on the principle of sufficient reason, § 20, p. 44 (third edition, p. 45). This confusion is to be found in its most aggravated form in Maine de Biran's book mentioned above, and this is dealt with more fully in the place last referred to; but apart from this it is also very common; for example, when people seek for the cause of any original force, such as gravitation. Kant himself (Über den Einzig Möglichen Beweisgrund, vol. i. p. 211-215 of Rosenkranz's edition) calls the forces of nature “efficient causes,” and says “gravity is a cause.” Yet it is impossible to see to the bottom of his thought so long as force and cause are not distinctly recognised as completely different. But the use of abstract conceptions leads very easily to their confusion if the consideration of their origin is set aside. The knowledge of causes and effects, always perceptive, which rests on the form of the understanding, is neglected in order to stick to the abstraction cause. In this way alone is the conception of causality, with all its simplicity, so very frequently wrongly apprehended. Therefore even in Aristotle (“Metaph.,” iv. 2) we find causes divided into four classes which are utterly falsely, and indeed crudely conceived. Compare with it my classification of causes as set forth for the first time in my essay on sight and colour, chap. 1, and touched upon briefly in the sixth paragraph of the first volume of the present work, but expounded at full length in my prize essay on the freedom of the will, p. 30-33. Two things in nature remain untouched by that chain of causality which stretches into [pg 218] infinity in both directions; these are matter and the forces of nature. They are both conditions of causality, while everything else is conditioned by it. For the one (matter) is that in which the states and their changes appear; the other (forces of nature) is that by virtue of which alone they can appear at all. Here, however, one must remember that in the second book, and later and more thoroughly in “The Will in Nature,” the natural forces are shown to be identical with the will in us; but matter appears as the mere visibility of the will; so that ultimately it also may in a certain sense be regarded as identical with the will.

On the other hand, not less true and correct is what is explained in § 4 of the first book, and still better in the second edition of the essay on the principle of sufficient reason at the end of § 21, p. 77 (third edition, p. 82), that matter is causality itself objectively comprehended, for its entire nature consists in acting in general, so that it itself is thus the activity (ενεργεια = reality) of things generally, as it were the abstraction of all their different kinds of acting. Accordingly, since the essence, essentia, of matter consists in action in general, and the reality, existentia, of things consists in their materiality, which thus again is one with action in general, it may be asserted of matter that in it existentia and essentia unite and are one, for it has no other attribute than existence itself in general and independent of all fuller definitions of it. On the other hand, all empirically given matter, thus all material or matter in the special sense (which our ignorant materialists at the present day confound with matter), has already entered the framework of the forms and manifests itself only through their qualities and accidents, because in experience every action is of quite a definite and special kind, and is never merely general. Therefore pure matter is an object of thought alone, not of perception, which led Plotinus (Enneas II., lib. iv., c. 8 & 9) and Giordano Bruno (Della Causa, dial. 4) to make the paradoxical assertion that [pg 219] matter has no extension, for extension is inseparable from the form, and that therefore it is incorporeal. Yet Aristotle had already taught that it is not a body although it is corporeal: “σωμα μεν ουκ αν ειη, σωματικη δε” (Stob. Ecl., lib. i., c. 12, § 5). In reality we think under pure matter only action, in the abstract, quite independent of the kind of action, thus pure causality itself; and as such it is not an object but a condition of experience, just like space and time. This is the reason why in the accompanying table of our pure a priori knowledge matter is able to take the place of causality, and therefore appears along with space and time as the third pure form, and therefore as dependent on our intellect.

This table contains all the fundamental truths which are rooted in our perceptive or intuitive knowledge a priori, expressed as first principles independent of each other. What is special, however, what forms the content of arithmetic and geometry, is not given here, nor yet what only results from the union and application of those formal principles of knowledge. This is the subject of the “Metaphysical First Principles of Natural Science” expounded by Kant, to which this table in some measure forms the propædutic and introduction, and with which it therefore stands in direct connection. In this table I have primarily had in view the very remarkable parallelism of those a priori principles of knowledge which form the framework of all experience, but specially also the fact that, as I have explained in § 4 of the first volume, matter (and also causality) is to be regarded as a combination, or if it is preferred, an amalgamation, of space and time. In agreement with this, we find that what geometry is for the pure perception or intuition of space, and arithmetic for that of time, Kant's phoronomy is for the pure perception or intuition of the two united. For matter is primarily that which is movable in space. The mathematical point cannot even be conceived as movable, as Aristotle has shown (“Physics,” vi. 10). This philosopher also himself [pg 220] provided the first example of such a science, for in the fifth and sixth books of his “Physics” he determined a priori the laws of rest and motion.

Now this table may be regarded at pleasure either as a collection of the eternal laws of the world, and therefore as the basis of our ontology, or as a chapter of the physiology of the brain, according as one assumes the realistic or the idealistic point of view; but the second is in the last instance right. On this point, indeed, we have already come to an understanding in the first chapter; yet I wish further to illustrate it specially by an example. Aristotle's book “De Xenophane,” &c., commences with these weighty words of Xenophanes: “Αϊδιον ειναι φησιν, ει τι εστιν, ειπερ μη ενδεχεται γενεσθαι μηδεν εκ μηδενος.” (Æternum esse, inquit, quicquid est, siquidem fieri non potest, ut ex nihilo quippiam existat.) Here, then, Xenophanes judges as to the origin of things, as regards its possibility, and of this origin he can have had no experience, even by analogy; nor indeed does he appeal to experience, but judges apodictically, and therefore a priori. How can he do this if as a stranger he looks from without into a world that exists purely objectively, that is, independently of his knowledge? How can he, an ephemeral being hurrying past, to whom only a hasty glance into such a world is permitted, judge apodictically, a priori and without experience concerning that world, the possibility of its existence and origin? The solution of this riddle is that the man has only to do with his own ideas, which as such are the work of his brain, and the constitution of which is merely the manner or mode in which alone the function of his brain can be fulfilled, i.e., the form of his perception. He thus judges only as to the phenomena of his own brain, and declares what enters into its forms, time, space, and causality, and what does not. In this he is perfectly at home and speaks apodictically. In a like sense, then, the following table of the Prædicabilia a priori of time, space, and matter is to be taken:—

Prædicabilia A Priori.

Of Time.Of Space.Of Matter.
(1) There is only one Time, and all different times are parts of it.(1) There is only one Space, and all different spaces are parts of it.(1) There is only one Matter, and all different materials are different states of matter; as such it is called Substance.
(2) Different times are not simultaneous but successive.(2) Different spaces are not successive but simultaneous.(2) Different matters (materials) are not so through substance but through accidents.
(3) Time cannot be thought away, but everything can be thought away from it.(3) Space cannot be thought away, but everything can be thought away from it.(3) Annihilation of matter is inconceivable, but annihilation of all its forms and qualities is conceivable.
(4) Time has three divisions, the past, the present, and the future, which constitute two directions and a centre of indifference.(4) Space has three dimensions—height, breadth, and length.(4) Matter exists, i.e., acts in all the dimensions of space and throughout the whole length of time, and thus these two are united and thereby filled. In this consists the true nature of matter; thus it is through and through causality.
(5) Time is infinitely divisible.(5) Space is infinitely divisible.(5) Matter is infinitely divisible.
(6) Time is homogeneous and a Continuum, i.e., no one of its parts is different from the rest, nor separated from it by anything that is not time.(6) Space is homogeneous and a Continuum, i.e., no one of its parts is different from the rest, nor separated from it by anything that is not space.(6) Matter is homogeneous and a Continuum, i.e., it does not consist of originally different (homoiomeria) or originally separated parts (atoms); it is therefore not composed of parts, which would necessarily be separated by something that was not matter.
(7) Time has no beginning and no end, but all beginning and end is in it.(7) Space has no limits, but all limits are in it.(7) Matter has no origin and no end, but all coming into being and passing away are in it.
(8) By reason of time we count.(8) By reason of space we measure.(8) By reason of matter we weigh.
(9) Rhythm is only in time.(9) Symmetry is only in space.(9) Equilibrium is only in matter.
(10) We know the laws of time a priori.(10) We know the laws of space a priori.(10) We know the laws of the substance of all accidents a priori.
(11) Time can be perceived a priori, although only in the form of a line.(11) Space is immediately perceptible a priori.(11) Matter can only be thought a priori.
(12) Time has no permanence, but passes away as soon as it is there.(12) Space can never pass away, but endures through all time.(12) The accidents change; the substance remains.
(13) Time never rests.(13) Space is immovable.(13) Matter is indifferent to rest and motion, i.e., it is originally disposed towards neither of the two.
(14) Everything that exists in time has duration.(14) Everything that exists in space has a position.(14) Everything material has the capacity for action.
(15) Time has no duration, but all duration is in it, and is the persistence of what is permanent in contrast with its restless course.(15) Space has no motion, but all motion is in it, and it is the change of position of what is moved, in contrast with its unbroken rest.(15) Matter is what is permanent in time and movable in space; by the comparison of what rests with what is moved we measure duration.
(16) All motion is only possible in time.(16) All motion is only possible in space.(16) All motion is only possible to matter.
(17) Velocity is, in equal spaces, in inverse proportion to the time.(17) Velocity is, in equal times, in direct proportion to the space.(17) The magnitude of the motion, the velocity being equal, is in direct geometrical proportion to the matter (mass).
(18) Time is not measurable directly through itself, but only indirectly through motion, which is in space and time together: thus the motion of the sun and of the clock measure time.(18) Space is measurable directly through itself, and indirectly through motion, which is in time and space together; hence, for example, an hour's journey, and the distance of the fixed stars expressed as the travelling of light for so many years.(18) Matter as such (mass) is measurable, i.e., determinable as regards its quantity only indirectly, only through the amount of the motion which it receives and imparts when it is repelled or attracted.
(19) Time is omnipresent. Every part of time is everywhere, i.e., in all space, at once.(19) Space is eternal. Every part of it exists always.(19) Matter is absolute. That is, it neither comes into being nor passes away, and thus its quantity can neither be increased nor diminished.
(20) In time taken by itself everything would be in succession.(20) In space taken by itself everything would be simultaneous.(20, 21) Matter unites the ceaseless flight of time with the rigid immobility of space; therefore it is the permanent substance of the changing accidents. Causality determines this change for every place at every time, and thereby combines time and space, and constitutes the whole nature of matter.
(21) Time makes the change of accidents possible.(21) Space makes the permanence of substance possible.
(22) Every part of time contains all parts of matter.(22) No part of space contains the same matter as another.(22) For matter is both permanent and impenetrable.
(23) Time is the principium individuationis.(23) Space is the principium individuationis.(23) Individuals are material.
(24) The now has no duration.(24) The point has no extension.(24) The atom has no reality.
(25) Time in itself is empty and without properties.(25) Space in itself is empty and without properties.(25) Matter in itself is without form and quality, and likewise inert, i.e., indifferent to rest or motion, thus without properties.
(26) Every moment is conditioned by the preceding moment, and is only because the latter has ceased to be. (Principle of sufficient reason of existence in time.—See my essay on the principle of sufficient reason.)(26) By the position of every limit in space with reference to any other limit, its position with reference to every possible limit is precisely determined. (Principle of sufficient reason of existence in space.)(26) Every change in matter can take place only on account of another change which preceded it; and therefore a first change, and thus also a first state of matter, is just as inconceivable as a beginning of time or a limit of space. (Principle of sufficient reason of becoming.)
(27) Time makes arithmetic possible.(27) Space makes geometry possible.(27) Matter, as that which is movable in space, makes phoronomy possible.
(28) The simple element in arithmetic is unity.(28) The simple element in geometry is the point.(28) The simple element in phoronomy is the atom.

Notes to the Annexed Table.

(1) To No. 4 of Matter.

The essence of matter is acting, it is acting itself, in the abstract, thus acting in general apart from all difference of the kind of action: it is through and through causality. On this account it is itself, as regards its existence, not subject to the law of causality, and thus has neither come into being nor passes away, for otherwise the law of causality would be applied to itself. Since now causality is known to us a priori, the conception of matter, as the indestructible basis of all that exists, can so far take its place in the knowledge we possess a priori, inasmuch as it is only the realisation of an a priori form of our knowledge. For as soon as we see anything that acts or is causally efficient it presents itself eo ipso as material, and conversely anything material presents itself as necessarily active or causally efficient. They are in fact interchangeable conceptions. Therefore the word “actual” is used as synonymous with “material;” and also the Greek κατ᾽ ενεργειαν, in opposition to κατα δυναμιν, reveals the same source, for ενεργεια signifies action in general; so also with actu in opposition to potentia, and the English “actually” for “wirklich.” What is called space-occupation, or impenetrability, and regarded as the essential predicate of body (i.e. of what is material), is merely that kind of action which belongs to all bodies without exception, the mechanical. It is this universality alone, by virtue of which it belongs to the conception of body, and follows a priori from this conception, and therefore cannot be thought away from it without doing away with the conception itself—it is this, I say, that distinguishes it from any other kind of action, such as that of electricity or chemistry, or light or heat. Kant has very accurately analysed this space-occupation of the mechanical mode of activity into repulsive and attractive force, just as a given mechanical force is analysed into two others by means of the parallelogram of forces. But this is really only the thoughtful analysis of the phenomenon into its two constituent parts. The two forces in conjunction exhibit the body within its own limits, that is, in a definite volume, while the one alone would diffuse it into infinity, and the other alone would contract it to a point. Notwithstanding this reciprocal balancing or neutralisation, the body still acts upon other bodies which contest its space with the first force, repelling them, and with the other force, in gravitation, attracting all bodies in general. So that the two forces are not extinguished in their product, as, for instance, two equal forces acting in different directions, or +E and -E, or oxygen and hydrogen in water. That impenetrability and gravity really exactly coincide is shown by their empirical inseparableness, in that the one never appears without the other, although we can separate them in thought.

I must not, however, omit to mention that the doctrine of Kant referred to, which forms the fundamental thought of the second part of his “Metaphysical First Principles of Natural Science,” thus of the Dynamics, was distinctly and fully expounded before Kant by Priestley, in his excellent “Disquisitions on Matter and Spirit,” § 1 and 2, a book which appeared [pg 225] in 1777, and the second edition in 1782, while Kant's work was published in 1786. Unconscious recollection may certainly be assumed in the case of subsidiary thoughts, flashes of wit, comparisons, &c., but not in the case of the principal and fundamental thought. Shall we then believe that Kant silently appropriated such important thoughts of another man? and this from a book which at that time was new? Or that this book was unknown to him, and that the same thoughts sprang up in two minds within a short time? The explanation, also, which Kant gives, in the “Metaphysical First Principles of Natural Science” (first edition, p. 88; Rosenkranz's edition, p. 384), of the real difference between fluids and solids, is in substance already to be found in Kaspar Freidr. Wolff's “Theory of Generation,” Berlin 1764, p. 132. But what are we to say if we find Kant's most important and brilliant doctrine, that of the ideality of space and the merely phenomenal existence of the corporeal world, already expressed by Maupertuis thirty years earlier? This will be found more fully referred to in Frauenstädt's letters on my philosophy, Letter 14. Maupertuis expresses this paradoxical doctrine so decidedly, and yet without adducing any proof of it, that one must suppose that he also took it from somewhere else. It is very desirable that the matter should be further investigated, and as this would demand tiresome and extensive researches, some German Academy might very well make the question the subject of a prize essay. Now in the same relation as that in which Kant here stands to Priestley, and perhaps also to Kaspar Wolff, and Maupertuis or his predecessor, Laplace stands to Kant. For the principal and fundamental thought of Laplace's admirable and certainly correct theory of the origin of the planetary system, which is set forth in his “Exposition du Système du Monde,” liv. v. c. 2, was expressed by Kant nearly fifty years before, in 1755, in his “Naturgeschichte und Theorie des Himmels,” and more fully in 1763 in his “Einzig möglichen Beweisgrund des Daseyns Gottes,” ch. 7. Moreover, in the later work he gives us to understand that Lambert in his “Kosmologischen Briefen,” 1761, tacitly adopted that doctrine from him, and these letters at the same time also appeared in French (Lettres Cosmologiques sur la Constitution de l'Univers). We are therefore obliged to assume that Laplace knew that Kantian doctrine. Certainly he expounds the matter more thoroughly, strikingly, and fully, and at the same time more simply than Kant, as is natural from his more profound astronomical knowledge; yet in the main it is to be found clearly expressed in Kant, and on account of the importance of the matter, would alone have been sufficient to make his name immortal. It cannot but disturb us very much if we find minds of the first order under suspicion of dishonesty, which would be a scandal to those of the lowest order. For we feel that theft is even more inexcusable in a rich man than in a poor one. We dare not, however, be silent; for here we are posterity, and must be just, as we hope that posterity will some day be just to us. Therefore, as a third example, I will add to these cases, that the fundamental thoughts of the “Metamorphosis of Plants,” by Goethe, were already expressed by Kaspar Wolff in 1764 in his “Theory of Generation,” p. 148, 229, 243, &c. Indeed, is it otherwise with the system of gravitation? the discovery of which is on the Continent of Europe always ascribed to Newton, while in England the learned at least know very well that it belongs to Robert Hooke, who in the year 1666, in a “Communication to the Royal Society,” expounds it quite distinctly, although only as an hypothesis and without proof. The [pg 226] principal passage of this communication is quoted in Dugald Stewart's “Philosophy of the Human Mind,” and is probably taken from Robert Hooke's Posthumous Works. The history of the matter, and how Newton got into difficulty by it, is also to be found in the “Biographie Universelle,” article Newton. Hooke's priority is treated as an established fact in a short history of astronomy, Quarterly Review, August 1828. Further details on this subject are to be found in my “Parerga,” vol. ii., § 86 (second edition, § 88). The story of the fall of an apple is a fable as groundless as it is popular, and is quite without authority.