We have therefore set down the terms the philosophers employ in matters of divinity, natural philosophy, and—only sparingly—in mathematics. These definitions are to be regarded as no more than explanations of the names: if demonstration establishes that the reality they describe is indeed as they describe it, one may treat the statement as a true definition; otherwise, it remains merely a clarification of the word.

Thus it is said, for example, that the jinn is “an aerial, rational animal, possessed of a subtle body, whose nature enables it to assume different forms.” Such a description is only an elucidation of the name as people commonly understand it. Whether a being of this sort actually exists must be established by proof: if proof confirms its existence, the statement counts as an essential definition; if proof does not, but instead shows that the ‘jinn’ referred to in the Sacred Law is something else, the description remains simply an explanation of the term in common usage.

Likewise, some define void by saying that it is “a spatial extension in which three dimensions can be posited, subsisting in no matter, such that a body may fill it and then vacate it.” Should evidence demonstrate that such a thing is impossible, this, too, is taken only as an explanation of the name as employed by speculative thinkers.

We have offered this preface to make it clear that any definitions we cite are intended merely to explain what the philosophers mean by their terminology, not to pronounce judgment that reality is exactly as they state. That judgment must await whatever demonstration establishes.

Refutation of al-Ghazali’s remarks

I say: What he observes about the difficulty of definition under the conditions he sets would indeed be correct—if the purpose of a definition were to provide a full mental portrayal of the defined essence, as they claim, and if such a thing were possible. Yet what they assert about definition is false, for it is impossible for the mere statement of a definition to yield a conception of the thing defined. Their alleged distinction between intrinsic, constitutive attributes that compose the essence and extrinsic, necessary attributes is baseless and without reality. Moreover, their demand that both kinds of attributes be included in definitions is precisely what the theologians forbid and refuse to allow. In truth, nothing here is either obligatory or forbidden, as we have explained elsewhere.