The heading “Being and thinking” names a distinction that is, so to speak, demanded by Being itself.

But in any case, such an intrinsic belonging of thinking to Being cannot be glimpsed on the basis of what we have offered so far as a characterization of thinking. Why not? Because we have not yet gained an adequate concept of thinking. But where can we get such a concept?

When we ask this, we are acting as if there had not already been a “logic” for centuries. It is the science of thinking, the doctrine of the rules of thinking and the forms of what is thought.Furthermore, it is the one philosophical science and discipline in which the standpoints and tendencies of worldviews play little or no part. Furthermore, logic counts as a secure, trustworthy science. It has taught the same thing since antiquity. True, one logician rearranges the structure and sequence of the various traditional doctrines; another leaves out this and that; still another makes additions from epistemology; another supports everything with psychology. But on the whole, a gratifying agreement prevails. Logic relieves us of the trouble of asking elaborate questions about the essence of thinking.

However, we would still like to raise one question. What does “logic” mean? The term is an abbreviation for ἐπιστήμη λογική, [92|128] the science of λόγος. And λόγος here means assertion. But logic is supposed to be the doctrine of thinking. Why is logic the science of assertion?

Why is thinking defined by assertion? This is by no means self-evident. Just above, we explicated “thinking” without reference to assertion and discourse. So meditation on the essence of thinking is a truly unique sort of meditation when it is undertaken as a meditation on λόγος, thereby becoming logic.