Hence, this universal judgment is not grasped by the senses alone but by a combination of sense-perception and reason—and the “sense” intended here is not merely hearing.

Some people group the whole of this category under the label “experiential knowledge,” whereas others divide it into two branches: experiential and intuitive. When the sensory data joined to reason arise from an act within a person’s power—such as eating, drinking, or taking medicine—they call it experiential. If they lie outside his control, like the changing phases of the moon when it faces the sun, they call it intuitive. The first terminology is closer to Arabic usage, for the Arabs describe a man as mujarrab (experienced) when events have tested and refined him, even though those events may be trials not of his own choosing.

Experience is gained through observation, scrutiny, and reflection: one notices a particular effect constantly accompanying a particular cause and comes to regard the pairing as a fixed habit. If he also perceives a fitting causal link, he adds that suitability to the constant concomitance, employing sabr wa-taqsīm—sifting and division—for these are indispensable in order to eliminate competing factors. Whenever the effect appears alongside two concomitants, attributing it to one rather than the other—or to both—has no warrant until the rival is ruled out.

The proofs jurists advance to establish that an attribute is the effective cause of a ruling—such as constant concomitance, suitability, and the like—fulfil their purpose only when competing causes have been excluded, and that is known through sabr wa-taqsīm. If that exclusion is merely probable, belief in the causality is likewise probable; if it is certain, the belief is certain—provided one is sure that the ruling must have a cause and that no other attribute can serve as that cause save the one identified.

Customary propositions in medicine and other sciences fall under this same heading, as do the propositions of grammar, morphology, and lexicography. In lexicography the meaning revolves around the word, whereas in grammar and morphology the rule revolves around the category. Thus we know that eating bread and the like satisfies hunger, drinking water and similar liquids quenches thirst, and wearing padded garments.