Yesterday The Donald proclaimed that, if elected this year, he would get 95% of the African-American vote in 2020. At first blush, this looks like typical Trumpian bushwah; he’s no more likely to get 95% of the African-American vote in any year than he is to become someone’s biological grandmother.

However, the propositional calculus of modern formal logic treats “if-then” statements in a fashion that leads to counter-intuitive results. “If X, then Y,” (formally, X ->Y) is interpreted to mean “It is not the case both that X is true and Y is false” (~[X and ~Y]). In the case where X is sometimes true, there’s no problem; the proposition claims that in all those cases, Y is also true, which is what we naturally mean when we say “if X, then Y.”

But a problem arises when X is always false. In that case, even if Y is never true, it is, indeed, never the case that X is true and Y is false, because it is never the case that X is true. Thus any “if-then” proposition counts as true when the “if” clause is false.

So, assuming that Donald Trump will not, in fact, win the Presidency this year, the claim that, *if* he were to win, *then* he would get 95% of the African-American vote in 2020 is also (trivially) true, just like the proposition that, *if* Trump were to win, *then* the Persians won Marathon andÂ Ï€ = 3.

Savor this moment; it may be the only instance this year when Donald Trump’s words express a true proposition. And it gives us all one more reason to work hard for the next 80 days: you wouldn’t want to make the poor man a *liar*, would you?