But we here leave to one side the findings of psychology concerning what it calls "ideas"; not because these findings are incorrect, let alone unimportant, but because they are scientific findings. For, being scientific statements, they are already operating in a realm which for psychology, too, must remain on that other side of which we spoke before. It is no cause for wonder, then, that within psychology it never becomes clear in any way what it is to which ideas are attributed and referred—to wit, the organism of living things, consciousness, the soul, the unconscious and all the depths and strata in which the realm of psychology is articulated. Here everything remains in question; and yet, the scientific findings are correct.

If we nonetheless leave science aside now in dealing with the question what it is to form ideas, we do so not in the proud delusion that we have all the answers, but out of discretion inspired by a lack of knowledge.

The word "idea" comes from the Greek εἴδω which means to see, face, meet, be face-to-face.

We stand outside of science. Instead we stand before a tree in bloom, for example—and the tree stands before us. The tree faces us. The tree and we meet one another, as the tree stands there and we stand face to face with it. As we are in this relation of one to the other and before the other, the tree and we are. This face-to-face meeting is not then, one of these "ideas" buzzing about in our heads. Let us stop here for a moment, as we would to catch our breath before and after a leap. For that is what we are now, men who have leapt, out of the familiar realm of science and even, as we shall see, out of the realm of philosophy. And where have we leapt? Perhaps into an abyss? No! Rather, onto some firm soil. Some? No! But on that soil upon which we live and die, if we are honest with ourselves. A curious, indeed unearthly thing that we must first leap onto the soil on which we really stand. When anything so curious as this

Martin Heidegger (GA 8) What Is Called Thinking?