Full Idea
It is hard or impossible to conceive of Caesar's not being a man (human).
Gist of Idea
It is hard or impossible to think of Caesar as not human
Source
David Wiggins (Sameness and Substance [1980], 4.5)
Book Reference
Wiggins,David: 'Sameness and Substance' [Blackwell 1980], p.117
A Reaction
So is it 'hard' or is it 'impossible'? Older generations of philosophers simply didn't read enough science fiction. Any short story could feature Caesar's failure to be a man. His assassination was a disaster for the Martian invasion of 44 BCE.