The Limits of Thought

The concrete can never be exhausted by thought since the concrete is never complete: by thinking the concrete, concrete is generated, and so on and so forth. The concrete is not frozen.

This can be expressed or mediated by several principles. Philosophers of the conservative type bring out analogia entis for this, but this is strictly non-necessary and leads to various metaphysical problems which I won't discuss here. Deleuze, largely following Leibniz, posits inexhaustible individuals ("differences") as what there are; in turn, this is a move that follows Scotus' "thisness" that argues that individuated beings differ more than in terms of material content. Kant's solution is in actual fact more advanced, though not often noticed. I shall not go into details but his point is roughly that differences are procedurally generated.
We may go further and utilize Goedel's theorem or Chaitin's theorem, etc., or diagonalization, to argue the point.

This is a truth that needs constant repetition: the concrete is not frozen and cannot be exhausted by any theory.

But equally important is the fact that even if the concrete is inexhaustible, it is to be thought and analyzed as much as possible. There's no justification in abandoning thought and plunge into willful ignorance and blind decision based on the fact that thought and theory cannot exhaust the concrete. It is impossible to avoid death doesn't mean there's no point in living. It is absolutely strange and absurd to argue (to think) that thinking is worthless since thinking cannot exhaust reality, and this position itself is precisely a claim to a final decision of the structure of reality.