Second: One might say that by “definition” (ḥadd) they intend the very thing defined, but that is not what they mean here. What they do mean is the verbal statement that indicates the quiddity of the thing defined—an expanded explanation of what the name conveys only in summary form.

So we say: If a definition is simply the statement uttered by the definer, then the definer must have come to know the thing either through another definition or without any definition at all. If it is the former, the same problem arises with the second definition as with the first, entailing either a prior circularity or an infinite regress of causes—both impossible by the consensus of rational people. If, however, he came to know it without a definition, their negative claim that “nothing is known except by means of a definition” collapses.

Third: All nations—scholars of doctrine, practitioners of crafts, and tradespeople alike—know the matters they must know and perfect the sciences and skills they practice without ever employing a single logical definition. None of the leading authorities in their fields—whether jurisprudence, grammar, medicine, mathematics, or the various crafts—speak in these technical definitions, yet they clearly grasp the individual concepts of their disciplines. It follows that conception is independent of such definitions.

Fourth: Up to this very hour no one has produced a single sound definition on their own principles. Even the most obvious example—“man,” defined as a “rational animal”—is riddled with the well-known objections, as are the definitions of the sun and the like. When later grammarians ventured into formal definitions they offered for “noun” more than twenty definitions, every one of them vulnerable to objection on their principles; indeed they produced as many as seventy definitions of “noun,” none of which proved valid, as the later Ibn al-Anbārī reports. Scholars of legal theory likewise proposed over twenty definitions for “analogy (qiyās),” all of them impeachable by the same standards. In truth, most definitions cited in the books of philosophers, physicians, grammarians, jurists, and theologians are flawed according to those very principles; and even if a few are claimed to be sound, they are exceedingly rare—virtually nonexistent. If conceptualizing things really depended on having such definitions, then to this moment people would not have conceived a single one of these matters. Since assent depends on conception, without conception there can be no assent, and humankind would possess no knowledge in the bulk of its sciences. That is the epitome of sophistry.