say anything about the nature of identity? No, at least not directly. Rather, the principle already presupposes what identity means and where it belongs. How do we get any information about this presupposition? The principle of identity itself gives it to us, if we listen carefully to its key note, if we think about that key note instead of just thoughtlessly mouthing the formula "A is A." For the proposition really says: "A is A.” What do we hear? With this “is,” the principle tells us how every being is, namely: it itself is the same with itself. The principle of identity speaks of the Being of beings. As a law of thought, the principle is valid only insofar as it is a principle of Being that reads: To every being as such there belongs identity, the unity with itself.
What the principle of identity, heard in its fundamental key, states is exactly what the whole of Western European thinking has in mind—and that is: the unity of identity forms a basic characteristic in the Being of beings. Everywhere, wherever and however we are related to beings of every kind, we find identity making its claim on us. If this claim were not made, beings could never appear in their Being. Accordingly, there would then also not be any science. For if science could not be sure in advance of the identity of its object in each case, it could not be what it is. By this assurance, research makes certain that its work is possible. Still, the leading idea of the identity of the object is never of any palpable use to the sciences. Thus, what is successful and fruitful about