Full Idea
Whether objects of a given kind should be thought actually to exist should, in general, be taken to turn on considerations of whether an inclusion of such objects in one's ontology has explanatory value.
Gist of Idea
Our commitment to the existence of objects should depend on their explanatory value
Source
E.J. Lowe (The Possibility of Metaphysics [1998], 2.3)
Book Reference
Lowe,E.J.: 'The Possibility of Metaphysics' [OUP 2001], p.39
A Reaction
Blatantly fictional objects, such as fairies, might have wonderful explanatory value (they place dewdrops on flowers). Our ontological commitments cannot be decided one at a time, because consistency of the whole picture is the key value.