And it is well known, as all rational people agree, that mentioning a shared universal together with some of its instances establishes it more firmly in the mind than mentioning it in isolation from all its instances.

For this reason, they say that the intellect follows sensory perception: when the senses perceive particulars, the intellect apprehends a universal feature common to them. Universals thus arise in the mind after particular instances have been known. Knowledge of particular instances is therefore among the most important means of knowing universals. How, then, could mentioning them weaken the reasoning, while omitting them would strengthen it? This is the distinctive function of the intellect: to know universals through knowledge of particulars. Whoever denies this denies the distinctive function of the human intellect. Anyone who maintains that mentioning universals without any of their particular instances is more effective than mentioning them alongside examples of those instances is obstinately denying the obvious.

Rational people agree that giving examples helps one understand universals, and that presenting a universal with an example is not the same as presenting it without one. Anyone who reflects on all the rationally known universals that people discuss in medicine, arithmetic, crafts, commerce, and other fields will find this to be the case.

A person may deny something until he sees a single instance of its kind; he then acknowledges the kind and thereby acquires a universal judgment. For this reason, Allah, glorified be He, says:

“The people of Noah denied the messengers.”

“Ād denied the messengers.”

And there are other similar statements. Only one messenger came to each of these peoples. Yet they rejected messengers as a class; their rejection was not directed specifically at that one messenger as an individual.