and crafts—know the things they need to know and master the sciences and practical activities in which they engage without articulating any definition. We find none of the leading authorities in the sciences employing these definitions: neither the authorities on jurisprudence, grammar, medicine or arithmetic, nor practitioners of the crafts. Yet they conceive the individual concepts of their disciplines. It is therefore clear that conception has no need of these definitions.

(Fourth: To this day, no definition is known that is sound according to their principles. Indeed, the most obvious of things is the human being, yet its definition as a “rational animal” is subject to the well-known objections. The same applies to the definition of the sun and similar things. Even the grammarians, when their later scholars ventured into definitions, offered twenty-odd definitions of the noun, all of which are open to objections according to their principles. Scholars of legal theory likewise offered twenty-odd definitions of analogical reasoning, all of which are also open to objections. Most definitions mentioned in the books of philosophers, physicians, grammarians, scholars of legal theory and speculative theologians are open to objections; only a few have escaped them. If conceiving things depended on definitions, people would not, to this day, have conceived any of these things. Assent depends on conception, so where no conception is attained, no assent is attained. Humanity would therefore possess no knowledge in most of its disciplines. This is sophistry of the highest order.

(Fifth: According to them, conception of an essence is attained only through a real definition composed of shared and distinguishing essential attributes—that is, one composed of genus and differentia. Such a definition is either impossible or difficult to formulate, as they themselves have acknowledged. In that case, no one would have conceived