Thus the Nicomachean Ethics begins by identifying the good with happiness (euSaeµovia), and happiness with virtuous action.
These considerations make it probable that the author of all three treatises was Aristotle himself; while the analysis of the treatises favours the hypothesis that he wrote the Eudemian Ethics and the Magna Moralia more or less together as the rudimentary first drafts of the mature Nicomachean Ethics.
As then we find this identification of pleasure with activity in the Metaphysics and in the De Anima, as well as in the Nicomachean Ethics, the Eudemian Ethics and the Magna Moralia, the only logical conclusion, from which there is no escape, is that, so far as the treatment of pleasure goes, any Aristotelian treatise which defines it as activity is genuine.
Moreover, the distinction between activity and pleasure in the tenth book is really fatal to the consistency of the whole Nicomachean Ethics, which started in the first book with the identification of happiness and virtuous activity.
It is further remarkable that the Nicomachean Ethics proceeds to a different conclusion.
