Term originally used by Ryle to refer to terms that occur in sentences about any kind of subject-matter. The logical constants are the clearest example. In the subsequent work of Smart, expressions that refer to things are topic-neutral if they leave open the substantive question of the kind of thing to which they are referring. ‘The person who killed her’ is not topic-neutral since it must be satisfied by a person, but ‘whoever or whatever caused the sound’ is, since what is referred to might be the wind, or a person, or anything else. See also Ramsey sentence, quiddity.
Philosophy dictionary. Academic. 2011.