What is virtue?

After Virtue is a book written by philosopher Alasdair MacIntyre, in which he argued that we no longer have a shared notion of virtue as a basis for argument. Because of this, he observed in the second edition of the book, "the culture of modernity lacks the resources to proceed further with its own moral enquiries." His definition of "virtue" is pretty similar Aristotle's concept of virtue. The best way to define this is that virtue is what contributes to living a good life. Like Aristotle, MacIntyre believes that virtue can really only be understood in social terms, in reference to "practices, traditions, and the narrative unity of human lives." The problem, which is beyond the scope of this answer to address, is that Aristotle, Thomas Aquinas, and some other philosophers who have shaped our understanding of virtue, thought that seeking virtue was a rational endeavor, in that people pursued some knowable end. MacIntyre claims that since the nineteenth century, philosophers have been unable to agree on the "standards of rational justification." This makes reasoned philosophical debate impossible until its participants are willing to recognize solutions to important questions in other philosophical traditions.