David Odden raised a very interesting point, that one could view Aristotle’s philosophy as ‘criticism’ of some tenets of Objectivism, in that Aristotle often explicitly states, and then argues against, some points which an Objectivist would support. Interestingly, though probably expectedly so, even back in the day of Ancient Greece the ideas that would lead to Objectivism as opposed to Aristotelianism were proposed, and discussed (and rejected, at the time, in favor of the latter). Although some would say that Aristotle was simply unaware, or that the Greek philosophy hadn’t advanced enough at the time to reach the Oist position, the truth is (often, but not always) quite the contrary.
Oftentimes in his Ethics and Politics Aristotle explicitly discusses and criticizes a some aspects of Oism’s stand on individualism, on relationship of man to society around him, on the proper purpose of government, etc. The two philosophies seem to also differ on the nature of virtue. From what I remember, for Objectivism virtue is an act; this, for example, would be Justice - “The boy pays for his candy.” A sum total of all his acts of acquiring the candy indicate the magnitude of his virtue/vice. So if he paid for the candy 75% of the time and stole it 25% of the time, he may be said to have obtained *some* justice. He’s 3/4s just. This is a quantitative approach.
For Aristotle (and Greeks at large) virtue is a habit, a state of mind more than any individual act - “The boy always pays for his candy.” If he only pays for it whenever he wants to he doesn’t really have the virtue of justice, even if he pays more often than not. So, for Aristotle, if the boy paid 75% of the time, he shouldn’t be considered to have any justice at all. He does a just act 75% of the time, but he does not have the habit of acting justly, given 25% theft. But then when virtues approach upper 90s, the reverse becomes true: if the boy pays for the candy 99% of the time, and steals 1%, he is said to have the virtue of justice, the habit of acting with fairness. This habit of his is broken rarely, and that’s the thing: he has the habit, the state of mind, that is just, and 1% of the time he does things contrary to it (as opposed to not having a just state of mind, even if doing a just thing most of the time). So at lower levels Aristotle would deny virtue quicker than Oism, but at upper levels he would grant virtue when Oism would deny it (Oism would say “the man who pays 99% of the time can’t be said to be truly just, only mostly just”).
But then again it could be argued that “nature of virtue” is not a proper subject for philosophy, but for other branches such as psychology or psycho-epistemology. But here Aristotle would disagree as well, for he defines philosophy as something like “a comprehensive study for finding rules that help man live qua man”. Thus, he would view the study of habits, today a part of psychology, properly a philosophical subject. For him, philosophy is not a detached (pigeonholed) academic subject - he’s not satisfied with knowing that ‘paying’ is Just, he has to tie that to man’s nature and find out what makes a just man, and how to get more of it, not solely which of his acts could be labeled as Just, and which couldn’t. The causes and means for advancement in moral qualities (getting from Bad to Good) are just as important for him as the final result (“What is Good? Which man can be said to be Good?”).
Edit: I should add that there’s a good reason I put this topic in the Ethics forum. Politics forum seems to be more about concrete political structures, far from Aristotle’s interest, and Metaphysics/Epistemology are where Aristotle and AR meet without much incident, or where his disagreements are simply Platonic and not too convincing.
There are other interesting ways in which Aristotle and Oism disagree, and I don’t want to pigeonhole this entire thread to be a discussion about the nature of virtue. Please be sure to raise other issues, once virtue has been sufficiently discussed.