It pains this old logic professor to read university officials’ arguments against divesting their institutions of investments in fossil fuels, not because their refusal to divest is wrong-headed, although I believe it is, but because their logic is so awful. A sample of Ivy League universities’ antidivestment statements offers a primer in the fallacies that students are warned against in Logic 101. Here are four: The ad hominem argument: "I find a troubling inconsistency in the notion that, as an investor, we should boycott [the oil-and-gas industry, while we] are extensively relying on those companies’ products and services," writes Drew Faust, president of Harvard University.