Many arguments in the corpus of mathematical anti-evolutionism are drawn from probability theory. We describe the basic mathematical ideas underlying probability, as well as the closely related branch of mathematics known as combinatorics. We then discuss and refute the major probabilistic arguments made by anti-evolutionists.

This article first appeared as a book chapter in the <italic>Handbook of Philosophy and Public Policy</italic>, edited by David Boonin and published by Palgrave in 2018. I was tasked with finding a test case of freedom of speech and inquiry from the sciences, in the larger context of free speech issues as related to public policy and the law. I have already written extensively about evolution and creationism, most notably in my 1997 book <italic>Why People Believe Weird Things</italic> and my 2006 book <italic>Why Darwin Matters</italic>, so here I engage the creationist movement as a free speech issue inasmuch as its proponents hold a minority viewpoint as far as the scientific community is concerned. Nevertheless, I contend that they should be free to believe, teach (and preach) whatever they like about the origins and diversity of life, and that, in the well-trodden principle, sunlight is the best disinfectant (to which Supreme Court Justice Louis Brandeis added “electric light the most efficient policeman”).