Dismayed by the recently announced list of “scholars and writers” supporting Trump for President, I sat down this morning to write a brief post explaining why I think supporting Trump is a very bad decision. But where to begin?

And then I thought: You all know who Trump is. You know that he’s a preening, vaunting, compulsively dishonest ignoramus with a mean streak a mile wide, whose only criterion for evaluating other human beings is: Do they like me? You are intelligent and well-informed. You can be under no illusions in these matters. And yet you not only will vote for Trump, you are warmly encouraging others to do the same.

Long ago Thomas Kuhn introduced into the history of science the concept of incommensurability: theories whose premises are so radically divergent that adherents of one theory simply cannot speak coherently and usefully with adherents of another. Alasdair MacIntyre would later, in After Virtue, apply this concept to debates in moral philosophy: “Every one of the arguments is logically valid or can be easily expanded so as to be made so; the conclusions do indeed follow from the premises. But the rival premises are such that we possess no rational way of weighing the claims of one as against another…. It is precisely because there is in our society no established way of deciding between these claims that moral argument appears to be necessarily interminable.”

If an intelligent and well-informed person is not only voting for Trump but also advocating for him as someone who can “restore the promise of America,” then it is clear that our premises about politics — about what politics does, what politics is for — are so radically different as to be incommensurable. (Ditto our notions  of what “the promise of America” is.) It was MacIntyre’s hope in After Virtue and the books that succeeded it to find a way around or through the impasse of incommensurability in moral philosophy. Until someone can do the same for the politics of this current election, there is no possibility of my even having a meaningful conversation with the people who signed that document. And as another philosopher has sagely counseled, What we cannot speak about we must pass over in silence.