Full Idea
From the fact that an object is truly described as "a man", it follows that you ought to accept relevantly similar objects as men.
Gist of Idea
If this is a man, you ought to accept similar things as men
Source
John Searle (Rationality in Action [2001], Ch.5.IV)
Book Reference
Searle,John R.: 'Rationality in Action' [MIT 2001], p.160
A Reaction
'Similar' rather begs the question. Common speech distinguishes sharply between a man and a 'real man'. You only accept them as men if you see them as men, not as similar to something else. Interesting.