Wikipedia defines Bulverism as the practice of assuming a speaker’s argument is invalid and then explaining why the speaker came to make that mistake.
TV Tropes defines it as the practice of saying “You’re only claiming X to be the case because you want X to be the case!”
It is a silly word. It was made up by C.S. Lewis in order to make fun of a silly mistake sometimes made by silly people. He mentions it only once, in a light-hearted introduction to a serious religious lecture. He doesn’t use it consistently. Sometimes Bulverism is a rather dishonest rhetorical trick; sometimes it is a logical fallacy; and sometimes it is a very serious metaphysical error.
But Lewis’s silly word is frequently used seriously by conservative Christians. If you ever dare utter the phrase “you only think that because...” then someone from the American Internet will pop up and accuse you of Bulverism.
The website WriteAtHome uses the word to describe any allegation of conscious or unconscious bias. Do you think that a set of statistics about the benefits of home schooling may be skewed because they were collected by an organisation which exists to promote home schooling? You are guilty of Bulverism. Wonder if a certain individual wants government spending on state schools reduced because they happen to run a private tutoring business? You’re a Bulverist. Suggest on the other hand that state school teachers want the state education system to carry on so they can keep their jobs? Stop Bulverizing.
Another site, StandToReason (“Clear thinking about Christianity”) applies the word to claims that there are psychological or sociological components in the formation of religious belief. “You believe that Christianity is true because you were born in a Christian community”. Bulverism. “You believe that Christianity is true because you need a psychological crutch”. Bulverism.
A more extreme example comes from an essay called The Creepy Normalisation of Bulverism on a website called Intellectual Take Out. (I wonder if the writer really meant “creeping”?) It seems that Karl Marx, Sigmund Freud, Jacques Lacan, the Frankfurt School, Jacques Deriedda, Cultural Marxism and identity politics—henceforth known as “the usual suspects”—were all Bulverists. At any rate, they have created a culture in which “people of even moderately conservative views are fair game to be Bulverized”. It seems that leftists assume that the motives of the “oppressed” (with scare quotes) are always good and the motives of the non-oppressed (without quotes) are always bad. And this was what Lewis was warning us about. “You only say that because you’re (white) (Christian) (a man) (cis)!” is the go- to example of Bulverism.
It is true that in each case, someone has used “you only say that because...” as a rhetorical formula: you think that home-schoolers get good academic results because you support home-schooling; you believe in Christianity because you have a psychological or spiritual need for support; you don’t believe in the existence of racist micro-aggressions because you are a white person. But are all these cases fallacies? Are they all the same kind of fallacy? And are they the kind of fallacy that C.S. Lewis was making fun of?