Let us anticipate the problematic and delineate it in a general way. Kant says: The unity of all combining—and thus the possibility of combinability at all—is grounded in the transcendental apperception, the “I think.” So now we confront the question: What is the condition of the possibility of the determinability of time as such in an “I think”? Or even more precisely: What is the condition of the possibility that time as such and an “I think” be together? Let me stress: I am radicalizing the problematic of Kant’s Critique in terms of this question. If you say that this question cannot be found in the Critique, I readily admit you are right. But we must ask whether this is not the question that first makes the entire problematic of the Critique intelligible.

In his Cartesian way, Kant thinks that everything that can be demonstrated as prior (a priori) in what is known in an act of knowing must belong to the subject. This means that time, as an intuition, is something that already operates in the mind; and it means that the “I think” is an act of spontaneity of the mind. Thus the question becomes that of the connection between time qua intuition and the “I think”—both as determinations of the mind. It becomes the question about the basic context of [310] subjectivity, or as I would say: of human existence. It is quite clear in Kant’s research that he unquestionably had in mind this horizon that I have just been explaining. Both in his doctrine of schematism (B 180–181), where he deals with the action of time, as well as in the Transcendental Deduction, where he deals with the “I think” and synthesis, Kant says that the state of affairs is veiled and obscure. But he lets these contexts remain in their hiddenness.

Let me repeat once more: This is about the conditions of the possibility of a conjunction between time as such and the “I think” as such. On the one hand time is the form of the manifold that underlies all acts of thinking qua determining; and on the other hand the “I think” is what must be presupposed as providing a possible unity to every act of combining in thought. The two fundamental elements—pure manifold as such and pure unity as such, both of them as the a priori of a determinability as such—this is the problem that underlies the real issue in Kant’s investigation. Only if we pose the question in this way, i.e., about the conditions of the possibility of the ontological connection between both determinations of the mind (namely, time as pure intuition and the “I think” as an act of the mind’s spontaneity), do we comprehend the question philosophically. But at the same time that entails something else, namely: Yes, interpreting this ontological connection between time and the “I think” is the basic task; but on the other hand, I can put this task in motion only if, in asking about the being of this ontological connection, I have a clear notion of what being in general means.

Post-Kantian Idealism also attempted to solve the problem of the unity of sensibility and understanding. However, in trying to do so, it