MacIntyre's ethics: justification and metaphysics

Following my summary of After Virtue, I want to dig deeper into some of the questions that arose in the discussion. One of these was how does MacIntyre justify his own account of morality in a way different to Nietzsche.

One of the commenters had the following to say:

Telos ethics is rooted in the concrete relationships one has as embedded in a particular community. Your values arise from your narrative embedded in that community, and those values are not up to you; it is not a matter of personal preference what those values are. So if you play chess growing up, you do not get to decide what the values of chess are. You must submit to the objective values of chess.

I followed up on this interpretation this by reading MacIntyre’s Search for a Defensible Aristotelian Ethics and the Role of Metaphysics by Marian Kuna, and the commenter’s take basically seems to be correct.

Moreover, there were some other useful extracts in Kuna’s paper touching on matters which I did not cover adequately in my summary.

First, regarding why the Aristotelian framework, and particularly its metaphysics, was rejected:

However, once the modern science of Galileo and Newton discredited Aristotelian physics, Aristotelian teleological explanatory framework was replaced by a mechanistic view of nature in which there is no place for natural ends, and so the rest of the Aristotelian scheme could not remain unaffected either.9 The Aristotelian final cause appeared to this new physics, predominantly concerned only with measurable aspects of physical reality, only as an outmoded relic of the past (MacIntyre 1985, 50–61, 81, 83). Therefore, the coexistence of non-teleological physics and teleological ethics became a serious problem.

Once the modern mechanistic science does not, and even cannot, understand physical movement and change in terms of the actualization of object’s potentia- lity toward its final cause, ‘human objects’ cannot be seen as aspiring to achieve their final causes either.

MacIntyre of course sought to create a non-metaphysical ethics, but later abandoned that quest and embraced a Thomist view. But interestingly, he was probably never on the road to success on this anyway:

However, Achtenberg does not claim just that Aristotle’s ethics is immune to criticism of this sort, she extends her critique of MacIntyre, claiming that his Aristotelian ethics is in fact as metaphysical as was Aristotle’s or, as she puts it, MacIntyre’s ethics “has every metaphysical commitment that he imputes to Aristotle”

MacIntyre’s definition of virtue as an acquired human quality, which if posses- sed and exercised by an individual, allows him/her to achieve those goods that are internal to various complex activities s/he is engaged in. Achtenberg rightly points to the fact that an exercisable quality “is at least a capacity and possibly disposition”, and so this definition is clearly metaphysical as it “requires some account of potentiality and act