But the “subject” originally, and still throughout the entire Middle Ages, does not have the least to do with the concept of the I and self of the human being. Quite the contrary. Subjectum is the translation of the Greek ὑποκείμενον, and this means everything that already lies before us in advance, that we run into and come upon—that is, when we set about determining something about beings, and for the Greeks this means asserting something about them.
The fact that beings are characterized here as what we run into in our asserting is not accidental and stands in the most intimate connection with the essence of the inception of philosophy, that is, with the question of beings as a whole and as such. To begin with, let us note only this: subjectum originally designates precisely what we call an object today; and objectum, to the contrary, means in the Middle Ages what we grasp as represented and opposed to us in mere thought, what is intended subjectively in today’s sense. But now, how could the word subjectum take on precisely the opposite meaning, so that it no longer means what lies at hand over against the I, but the I itself, and only this?
If we have grasped the preceding account of Descartes’s procedure, the answer cannot be difficult to reach. For under the spell of his method, Descartes seeks something that lies at hand as indubitable and that cannot be doubted away again. But this thing that lies at hand is the “I” of the doubter himself. Thus the I is a subjectum in the old sense. But now, because the I is not just any subjectum, but the fundamental thing that lies at hand, the subjectum receives the fundamental meaning of “I.” The I is not only a subjectum simply, but also and for this very reason, the subjectum is originally “I.” From now on, “subject” becomes the term for the I. (The I as something present at hand = subjectum. The subject as a preeminent subjectum. Subjectum = I.) And now we understand that it is not an innocuous term; behind it there stands the entire way in which the priority of the mathematical method has been worked out in philosophy.
c) The substantive consequence of the predominance of the
mathematical conception of method: the failure to reach the
authentic self of man and the failure of the fundamental question of
philosophy. The advance decision of mathematical certainty
regarding truth and Being
The first piece of evidence, according to which the self was taken as I, and the I was taken as consciousness, is joined now by the conception of the self-qua-I as subjectum: something present at hand. And if the later efforts of German idealism aim so passionately at not allowing the I to appear as a thing, this proves only that the original approach to the I as subjectum forces one in advance to make these efforts—that the effort
Being and Truth
GA 36/37 p. 44