Full Idea
A philosophical account of a general sort is required of what it is for different tokens to be of the same type. To refuse to give such an account is to be a metaphysical ostrich.
Gist of Idea
Refusal to explain why different tokens are of the same type is to be an ostrich
Source
David M. Armstrong (Against 'Ostrich Nominalism' [1980], §1)
Book Reference
'Properties', ed/tr. Mellor,D.H. /Oliver,A [OUP 1997], p.104
A Reaction
This defines Ostrich Nominalism (a label Armstrong aims at Quine). I certainly sympathise with Armstrong. If there is no more to a class (a type) than just having members (tokens), nothing is explain. What is natural, essential, intensional etc.?