Full Idea
Aristotle shows an indecision between an intellectualist and a comprehensive account of eudaimonia. …It is because he is not sure who we are that he finds it difficult to say unequivocally in what our eudaimonia consists.
Gist of Idea
Aristotle is unsure about eudaimonia because he is unsure what people are
Source
comment on Aristotle (Nicomachean Ethics [c.334 BCE]) by Thomas Nagel - Aristotle on Eudaimonia p.8
Book Reference
'Essays on Aristotle's Ethics', ed/tr. Rorty,Amélie Oksenberg [University of California 1980], p.8
A Reaction
Aristotle is quite right to be unsure about what people are, given the fluidity of human nature, in comparison with other animals. He needs a stable core to human nature, and I think that exists.