The world does not, as Plato once thought, consist of ideas, of which we only perceive the shadows. Rather it is the outcome of ideas, conceptually as well as practically. The conceptual is both a manner to orientate in the world and the creative mental invention of new thoughts or devices. The practical side is reduced to ‘copying’ the mental products onto reality. And exactly there lies the particular problem as shows the case of the benzene ring:

The discoverer of the benzene formula, F.A. Kekulé, had a dream about a ring of snakes one night. When he woke up, the ring was still present in his memory. Fortunately, Kekulé was a chemist and so realized that this scheme was the solution to a couple of theoretical problems he was occupied with. It followed a long line of conceptual work to formally prove the insight, which resulted in the hexagonal scheme of benzene known as benzene ring.

What happened was that Kekulé had seen a scientific problem that he could not explain with what he already knew, that is, deductively. Neither he was able to connect the observed phenomena with the rules usually applied in these situations to create further explanations of already known regularities, that is, an inductive manner of reasoning. He simply took together two things that had not been interconnected before, a ring of snakes and the benzene formula, which is called abduction.