altogether. Rather, it is achieved for some people and at some times, but not others, just as it is through names. A definition sets out in detail what a name indicates in general. Thus, one cannot say that a name never conveys knowledge of the thing named, nor that it conveys such knowledge to everyone. The same applies to a definition.

If it is claimed that a definition is meant, by itself, to ensure that its listener conceives the essence of the thing defined, which he has not conceived except through the definer’s words, and that he conceives it merely through the definer’s statement—as some people, including certain logicians and others, suppose—then this is an error. It is like the error of someone who supposes that names necessarily convey knowledge of the things named to those who hear them merely through the utterance of those words.

This has been discussed at length in its proper place. We have explained the position held by the majority of speculative thinkers among Muslims, Jews, Christians, Magians, Sabians, and polytheists: definitions are intended to distinguish the thing defined from everything else. This distinction is achieved through a property inseparably associated with the thing defined in both directions: its presence entails the presence of the thing defined, and its absence entails its absence. This is the approach of Muslim speculative thinkers from all groups, such as Abū ‘Alī, Abū Hāshim, and others like them; and Abū al-Hasan al-Ash‘arī, al-Qādī Abū Bakr, Abū al-Ma‘ālī al-Juwaynī, al-Qādī Abū Ya‘lā, Abū al-Wafā’ Ibn ‘Aqīl, and others like them.