mentioning some of its individual instances is more firmly impressed upon the intellect than citing it stripped of every instance—this is unanimously acknowledged by rational people.

For that reason they say: in proportion to its perception of particulars, the intellect discerns among them a universal common element; universals are formed in the soul only after the apprehension of definite particulars, and the knowledge of those particulars is one of the greatest means to knowing universals. How, then, could mentioning them weaken the analogy, while omitting them would render it stronger? This would negate the very peculiarity of intellect, for the distinctive function of the intellect is to grasp universals by way of its knowledge of particulars. Whoever denies this denies the special faculty of human reason, and whoever maintains that stating universals without any of their concrete loci is stronger than stating them together with examples of those loci is merely being obstinate. All rational people agree that presenting a universal together with illustrative examples aids in understanding it, and that stating it with examples is not the same as stating it devoid of all exemplification.

Whoever reflects on the range of universals known by reason—in medicine, mathematics, the natural sciences, the crafts, commerce, and so forth—will find the matter exactly so. When it is said, “The interior of the human body warms in winter and cools in summer because in winter the air is cold, cooling the body’s surface so that the heat withdraws to its interior—since a contrary flees from its contrary and a like is attracted to its like, cold manifests at the surface because what resembles a thing is drawn toward it,” this constitutes an unrestricted universal principle. When it is further said, “For this reason the earth’s interior warms in winter, as does the interior of every animal; and likewise cavities cool in summer because the surfaces are hot, so the cold retreats to the interior,” the more analogues a person considers, the stronger becomes his grasp of that universal: that the contrary flees from its contrary and the like is attracted to its like. This is acknowledged in physics, psychology, and other disciplines; yet when the analogues are mentioned, one’s knowledge of it grows more robust. This may also be expressed by saying that likeness is the cause of conjunction.

Similarly, when it is said, “When the sun strikes the sea or any other body, it heats it, and vapor rises because heat dissolves moisture,” and one then adds, “just as steam rises from a pot that contains hot water,”