What part does the third paragraph play in the passage?

Directions: Answer the question based on the following passage.

Mankind is not an entity, an organism, or a coral bush. The entity involved in production and trade is man. It is with the study of man – not of the loose aggregate known as a “community” – that any science of the humanities has to begin.

This issue represents one of the epistemological differences between the humanities and the physical sciences, one of the causes of the former’s well-earned inferiority complex in regard to the latter. A physical science would not permit itself (not yet, at least) to ignore or bypass the nature of its subject. Such an attempt would mean: a science of astronomy that gazed at the sky, but refused to study individual stars, planets, and satellites – or a science of medicine that studies disease, without any knowledge or criterion of health, and took, as its basic subject of study, a hospital as a whole never focusing on individual patients.

A great deal may be learned about society by studying man; but this process cannot be reversed: nothing can be learned about man by studying society – by studying the inter-relationships of entities one has never identified or defined. Yet that is the methodology adopted by most political economists. Their attitude, in effect, amounts to the unstated, implicit postulate: “Man is that which fits economic equations.” Since he obviously does not, this leads to the curious fact that in spite of the practical nature of their science, political economists are oddly unable to relate their abstractions to the concretes of actual existence.

It leads also to a baffling sort of double standard or double perspective in their way of viewing men and events: if they observe a shoemaker, they find no difficulty in concluding that he is working in order to make a living; but as political economists, on the tribal premise, they declare that his purpose (and duty) is to provide society with shoes. If they observe a panhandler on a street corner, they identify him as a bum; in political economy, he becomes “a sovereign consumer.” If they hear the communist doctrine that all property should belong to the state, they reject it emphatically and feel, sincerely, that they would fight communism to the death; but in political economy, they speak of the government’s duty to effect “a fair redistribution of wealth,” and they speak of businessmen as the best, most efficient trustees of the nation’s “natural resources.”

This is what a premise (and philosophical negligence) will do; this is what the tribal premise has done.

To reject that premise and begin at the beginning – in one’s approach to political economy and to the evaluation of various social systems – one must begin by identifying man’s nature, i.e., those essential characteristics which distinguish him from all other living species.