the convergence of the two categories in a single attribute?’ He makes no such claim. And if the challenger went on to ask, ‘Do you deny that by citing both attributes you have in fact succeeded in restricting the definiendum?’ he would have no grounds for denial. A definition, after all, does not impose a ruling; it simply discloses and clarifies. That function is accomplished by two attributes exactly as it is by one, so the whole discussion is no more than wrangling over phraseology.
Al-Qāḍī Abū Bakr ibn al-Ṭayyib said:
“If someone were to ask us, ‘What is your definition of knowledge?’ we would answer: ‘Knowledge is the cognition of the object of knowledge in accordance with what it truly is.’ The proof is that this definition confines knowledge to its proper meaning: nothing alien enters into it and nothing that belongs to it is left out. Whenever a definition thus surrounds the definiendum, it must be reckoned sound and established. Therefore, anything—knowledge or otherwise—that is defined by a statement which encloses the definiendum, distinguishes it from what is other than it, and embraces it as our definition does, must be acknowledged as correct. It is established that every piece of knowledge attaching to an object is cognition of that object as it really is, and every cognition of an object is knowledge of it. Hence the definition we have given, and have set forth as an explanation of its meaning, is necessarily a true definition of knowledge.”
I say: The Qāḍī has thus made it clear that any statement which so encompasses the definiendum that nothing extraneous enters it and nothing proper to it is left out constitutes a valid definition.
Al-Ghazālī’s acknowledgment of the difficulty of definition:
In his major work on logic, The Criterion of Knowledge, al-Ghazālī mentioned the theologians’ position after observing how resistant definition is according to the logicians’ method. He said:
Chapter Seven
On the resistance of definition to human capacity except at the utmost level of exertion and effort:
Whoever understands the sources of confusion in defining that we have pointed out will realize that human ability can guard against all of them only rarely. Those sources are numerous, and the four most stubborn for the mind are: