 Not only metaphysical assertions are generally set aside when pursuing natural language ontology. Philosophers when clarifying metaphysical intuitions make use only of certain sorts of expressions (or uses of expressions) and not others, and so for a linguist interested in the ontology of natural language. Certainly, they will not appeal to technical philosophical expressions or uses of expressions, that is, (uses of) expressions meant to convey philosophical notions arrived at by reflection, whether by philosophers or non-philosophers (the “folk”). It is a characteristic feature of natural language to allow for expansion, permitting at least certain types of expressions to be used with a particular intended meaning and to allow conveying new concepts through the formation of new expressions, by means of morphological processes or syntactic composition. These are entirely legitimate ways of using language, but they are generally set aside when philosophers appeal to language as a way of clarifying metaphysical intuitions. For example, Heidegger introduced the nominalization das Nichts “the nothing” as well as the verb nichten “to nothing”. While this is not an illegitimate use of language, no philosopher or linguist would take the existence of the nominalization or the verb to be evidence for there to be an entity that is a nothing or a corresponding process or state. Likewise, the possibility of forming, legitimately, the term the truth value true is certainly never taken as evidence for truth values being entities. Another example is the various meanings philosophers associate with the noun existence. The fact that there are different notions of existence that different philosophers endorse and associate as the meaning of the noun existence does not mean that the ontology of natural language reflects those notions all at once. As was mentioned in  Section 2.2.4,  not all expressions allow for “non-ordinary” or “philosophical” uses in that way. Expressions that belong to the functional part of grammar generally do not, such as auxiliaries (have, be, can, may), determiners, and quantifiers, and neither does the verb exist  (§1.3).