ON THE ESSENCE AND CONCEPT OF φύσις
subiectum, the ὑποκείμενον, and therefore about φύσις. The impossibility of getting around φύσις is shown in that name which we use to designate the kind of knowledge that, up until now, Westerners have had about beings as a whole. The systematic articulation of the truth at any given time "about" beings as a whole is called "metaphysics." It makes no difference whether or not this metaphysics is given expression in propositions, whether or not the expressions are formed into an explicit system. Metaphysics is that knowledge wherein Western historical humanity preserves the truth of its relations to beings as a whole and the truth about those beings themselves. In a quite essential sense, meta-physics is "physics," i.e., knowledge of φύσις (ἐπιστήμη φυσική).
At first blush our question about the essence and concept of φύσις might seem to be simply an inquiry, out of curiosity, into the origin of past and present interpretations of "nature." But if we consider that this fundamental word of Western metaphysics harbors within itself decisions about the truth of beings; if we recall that today the truth about beings as a whole has become entirely questionable; moreover, if we suspect that the essence of truth therefore remains thoroughly in dispute; and finally if we know that all this is grounded in the history of the interpretations of the essence of φύσις, then we stand outside the  merely historical interests that philosophy might have in the "history of a concept." Then we experience, although from afar, the nearness of future decisions.
[For the world is shifting out of joint — if indeed it ever was in joint — and the question arises whether modem humanity's planning, even if it be worldwide, can ever bring about the ordering of world.]
The first coherent and thoughtful discussion ("first" because of its way of questioning) of the essence of φύσις comes down to us from the time when Greek philosophy reached its fulfillment. It stems from Aristotle and is preserved in his φυσικὴ ἀκρόασις (Lectures given - or better, "Lectures heard" — on φύσις).
Aristotle's Physics is the hidden, and therefore never adequately studied, foundational book of Western philosophy.
Probably the eight books of the Physics were not projected as a unity and did not come into existence all at once. Such questions have no importance here. In general it makes little sense to say that the Physics precedes the Metaphysics, because metaphysics is just as much "physics" as physics is "metaphysics." For reasons based on the work itself, as well as on historical grounds, we can take it that around 347 B.C. (Plato's death) the second book