We will never know how many Catholics voted for Donald Trump. Suffice it to say that, whatever the number, it was uncomfortably large. Nor can we know the reasons for their deeply troubling choice. The best we can do is speculate, as Steven P. Millies does throughout his new book, Good Intentions. He does so intelligently, and I wouldn't quarrel with his conclusions. But since he does not address the important variables of age, class, gender, ethnic origins, and place of residence, his analysis does not run deep. He does do an excellent job, however, when it comes to the nation's bishops, who since 1973 have been more assertively political than at any time in our history. If Catholic voters are just as polarized as their non-Catholic fellow citizens, the bishops are at least partly to blame. Such is the message of Millies's book, and he makes a sturdy case.