Now these shapes and qualities which have been abstracted by us, are nothing but the peculiar, specially defined _way in which these bodies act_, which constitutes precisely their difference. If therefore we leave these shapes and qualities out of consideration, there remains nothing but _mere activity in general_, pure action as such, Causality itself, objectively thought--that is, the reflection of our own Understanding, the externalised image of its sole function; and Matter is throughout pure Causality, its essence is Action in general.[95] This is why pure Matter cannot be perceived, but can only be thought: it is a something we add to every reality, as its basis, in thinking it. For pure Causality, mere action, without any defined mode of action, cannot become perceptible, therefore it cannot come within any experience.--Thus Matter is only the objective correlate to pure Understanding; for it is Causality in general, and nothing else: just as the Understanding itself is direct knowledge of cause and effect, and nothing else. Now this again is precisely why the law of causality is not applicable to Matter itself: that is to say, Matter has neither beginning nor end, but is and remains permanent. For as, on the one hand, Causality is the indispensable condition of all alternation in the accidents (forms and qualities) of Matter, _i.e._ of all passage in and out of being; but as, on the other hand, Matter is pure Causality itself, as such, objectively viewed: it is unable to exercise its own power upon itself, just as the eye can see everything but itself. "Substance" and Matter being moreover identical, we may call _Substance_, _action_ viewed _in abstracto_: _Accidents_, particular modes of action, action _in concreto_.--Now these are the results to which true, _i.e._ transcendental, Idealism leads. In my chief work I have shown that the thing in itself--_i.e._ whatever, on the whole, exists independently of our representation--cannot be got at by way of representation, but that, to reach it, we must follow quite a different path, leading through the inside of things, which lets us into the citadel, as it were, by treachery.-- [95] Compare "Die Welt a. W. u. V." 2nd edition; vol. i. sect. 4, p. 9; and vol. ii. pp. 48, 49 (3rd edition, vol. i. p. 10; vol. ii. p. 52). English translation, vol. i. pp. 9-10; vol. ii. p. 218.