Conceptual Order
Concepts can be seen as having a certain order (analogous to the order of a capital good in economics)---concepts of the first order are those that are formed directly from perceptual data. From this basis one is capable of abstracting further and forming higher-level concepts:
A "first-level" concept, such as "table" or "man," is one formed directly from perceptual data. Starting from this base, concept-formation proceeds by a process of abstracting from abstractions. The result is (increasingly) higher-level concepts, which cannot be formed directly from perceptual data, but only from earlier concepts. For example, a child may integrate first-level concepts into wider ones, which identify more extensive knowledge, such as integrating "cat," "dog," "horse" into "animal" (and later, "animal," "plant," "man" into "living organism"). Or he may subdivide first-level concepts into narrower ones, which identify more precise differentiations, such as subdividing "man" according to profession, into "doctor," "policeman," "teacher" (and later "doctor" into "children's doctor," "dentist," "surgeon," etc.).[1]
What is important to keep in mind here, is that the ordering is provided by which concepts are required to form the further concepts---the lowest-level, most fundamental concepts, are those that are formed directly from percepts. The reason this is important is due to the tendency that exists wherein smaller is conflated with more fundamental---for instance, holding that quantum mechanics is the more real physics because the physics we directly observe is (said to be) borne from a result of quantum interactions; or that physics is more fundamental than chemistry because the chemical reactions are (said to be) borne from those same quantum interactions.
They, of course, neglect to provide any evidence that these physically smaller processes are more fundamental---i.e. that they are the primary cause and driving force behind such chemical reactions. Smaller does not mean more fundamental---certainly not in concept-formation. The fundamental building blocks of a conceptual apparatus are the ones that are provided by the specific sensory apparatus of the man in question.
Higher-level concepts represent a relatively advanced state of knowledge. They represent knowledge available only to a mind that has already engaged in the requisite conceptualization. For instance, a child just emerging from the perceptual period cannot start conceptualizing by uniting his father, his dog, and a rosebush into the concept "organism." Only when the child has first conceptualized separately the various perceptually given entities is he capable of the more extensive acts of abstraction and integration that identify their common denominators. These latter are not available on the perceptual level, because only concretes exist: there are no such things as "organisms" to be seen---there are only men, dogs, roses. Similarly, a child cannot identify distinctions among men--he cannot grasp types of men, such as doctor or teacher--until he has first grasped and conceptualized man.[2]