We also find *physics*, in the widest sense of the word, concerned with the explanation of phenomena in the world; but it lies already in the nature of the explanations themselves that they cannot be sufficient. *Physics* is unable to stand on its own feet, but needs a *metaphysics* on which to support itself, whatever fine airs it may assume towards the latter. For it explains phenomena by something still more unknown than are they, namely by laws of nature resting on forces of nature, one of which is also the vital force. Certainly the whole present condition of all things in the world or in nature must necessarily be capable of explanation from purely physical causes. But such an explanation―supposing one actually succeeded so far as to be able to give it―must always just as necessarily be burdened with two essential imperfections (as it were with two sore points, or like Achilles with the vulnerable heel, or the devil with the cloven foot). On account of these imperfections, everything so explained would still really remain unexplained. The first imperfection is that the *beginning* of the chain of causes and effects that explains everything, in other words, of the connected and continuous changes, can positively *never* be reached, but, just like the limits of the world in space and time, recedes incessantly and *in infinitum*. The second imperfection is that all the efficient causes from which everything is explained always rest on something wholly inexplicable, that is, on the original *qualities* of things and the *natural forces* that make their appearance in them. By virtue of such forces they produce a definite effect, e.g., weight, hardness, impact, elasticity, heat, electricity, chemical forces, and so on, and such forces remain in every given explanation like an unknown quantity, not to be eliminated at all, in an otherwise perfectly solved algebraical equation. Accordingly there is not a fragment of clay, however little its value, that is not entirely composed of inexplicable qualities. Therefore these two inevitable defects in every purely physical, i.e., causal, explanation indicate that such an explanation can be only *relatively* true, and that its whole method and nature cannot be the only, the ultimate and hence sufficient one, in other words, cannot be the method that will ever be able to lead to the satisfactory solution of the difficult riddles of things, and to the true understanding of the world and of existence; but that the *physical* explanation, in general and as such, still requires one that is *metaphysical*, which would furnish the key to all its assumptions, but for that very reason would have to follow quite a different path. The first step to this is that we should bring to distinct consciousness and firmly retain the distinction between the two, that is, the difference between *physics* and *metaphysics*. In general this difference rests on the Kantian distinction between *phenomenon* and *thing-in-itself*. Just because Kant declared the thing-in-itself to be absolutely unknowable, there was, according to him, no *metaphysics* at all, but merely immanent knowledge, in other words mere *physics*, which can always speak only of phenomena, and together with this a critique of reason which aspires to metaphysics."―from_The World as Will and Representation_. Translated from the German by E. F. J. Payne. In Two Volumes, Volume II, pp. 172-173
In consequence of the inevitably scattered and fragmentary nature of our thinking, which has been mentioned, and of the mixing together of the most heterogeneous representations thus brought about and inherent even in the noblest human mind, we really possess only *half a consciousness*. With this we grope about in the labyrinth of our life and in the obscurity of our investigations; bright moments illuminate our path like flashes of lighting. But what is to be expected generally from heads of which even the wisest is every night the playground of the strangest and most senseless dreams, and has to take up its meditations again on emerging from these dreams? Obviously a consciousness subject to such great limitations is little fitted to explore and fathom the riddle of the world; and to beings of a higher order, whose intellect did not have time as its form, and whose thinking therefore had true completeness and unity, such an endeavor would necessarily appear strange and pitiable. In fact, it is a wonder that we are not completely confused by the extremely heterogeneous mixture of fragments of representations and of ideas of every kind which are constantly crossing one another in our heads, but that we are always able to find our way again, and to adapt and adjust everything. Obviously there must exist a simple thread on which everything is arranged side by side: but what is this? Memory alone is not enough, since it has essential limitations of which I shall shortly speak; moreover, it is extremely imperfect and treacherous. The *logical ego*, or even the *transcendental synthetic unity of apperception*, are expressions and explanations that will not readily serve to make the matter comprehensible; on the contrary, it will occur to many that“Your wards are deftly wrought, but drive no bolts asunder.”Kant’s proposition: “The *I think* must accompany all our representations ,” is insufficient; for the “I” is an unknown quantity, in other words, it is itself a mystery and a secret. What gives unity and sequence to consciousness, since by pervading all the representations of consciousness, it is its substratum, its permanent supporter, cannot itself be conditioned by consciousness, and therefore cannot be a representation. On the contrary, it must be the *prius* of consciousness, and the root of the tree of which consciousness is the fruit. This, I say, is the *will*; it alone is unalterable and absolutely identical, and has brought forth consciousness for its own ends. It is therefore the will that gives unity and holds all its representations and ideas together, accompanying them, as it were, like a continuous ground-bass. Without it the intellect would have no more unity of consciousness than has a mirror, in which now one thing now another presents itself in succession, or at most only as much as a convex mirror has, whose rays converge at an imaginary point behind its surface. But it is *the will* alone that is permanent and unchangeable in consciousness. It is the will that holds all ideas and representations together as means to its ends, tinges them with the colour of its character, its mood, and its interest, commands the attention, and holds the thread of motives in its hand. The influence of these motives ultimately puts into action memory and the association of ideas. Fundamentally it is the will that is spoken of whenever “I” occurs in a judgement. Therefore, the will is the true and ultimate point of unity of consciousness, and the bond of all its functions and acts. It does not, however, itself belong to the intellect, but is only its root, origin, and controller."—from_The World as Will and Representation_. Translated from the German by E. F. J. Payne in two volumes: volume II, pp. 139-140
The most perfect and satisfactory knowledge is that of perception but this is limited to the absolutely particular, to the individual. The comprehension of the many and the various into *one* representation is possible only through the *concept*, in other words, by omitting the differences; consequently, the concept is a very imperfect way of representing things. The particular, of course, can also be apprehended immediately as a universal, namely when it is raised to the (Platonic) *Idea*; but in this process, which I have analysed in the third book, the intellect passes beyond the limits of individuality and therefore of time; moreover, this is only an exception.These inner and essential imperfections of the intellect are further increased by a disturbance to some extent external to it but yet inevitable, namely, the influence that the *will* exerts on all its operations, as soon as that will is in any way concerned in their result. Every passion, in fact every inclination or disinclination, tinges the objects of knowledge with its colour. Most common of occurrence is the falsification of knowledge brought about by desire and hope, since they show us the scarcely possible in dazzling colours as probable and well-nigh certain, and render us almost incapable of comprehending what is opposed to it. Fear acts in a similar way; every preconceived opinion, every partiality, and, as I have said, every interest, every emotion, and every predilection of the will act in an analogous manner.Finally, to all these imperfections of the intellect we must also add the fact that it grows old with the brain; in other words, like all physiological functions, it loses its energy in later years; in this way all its imperfections are then greatly increased.”—from_The World as Will and Representation_. Translated from the German by E. F. J. Payne in two volumes: volume II, pp. 139-141