In order to do inference, we constantly need to make use of categories and concepts: it is neither possible nor desirable to deal with every unique arrangement of quarks and leptons on an individual basis. Fortunately, because we don't live in a maximum-entropy universe of absolute chaos, we can talk about repeatable higher-level regularities in the world instead: we can distinguish particular configurations of matter as instantiations of object concepts like chair or human, and say that these objects have particular properties, like red or alive.
The sheer number of distinct configurations in which matter could be arranged is unimaginably vast, but the superexponential conceptspace of the number of different ways to categorize these possible objects is even vaster. If (for purposes of exposition) there are n objects in the world which either are, or are not instantiations of some concept, then the number of possible concepts is 2^n (for the mathematics involved, see powerset). Most of these possible concepts are complicated enough to be ruled out a priori by your prior; you can't expect to encounter enough evidence to cut down such a large space. The work of proper inference is to "carve reality at its joints"; to find simple generalizations and simple concepts that let you make useful inferences with respect to your goals.