Futuyma: Philosophers and scientists use “chance” only in the sense of unpredictability. Chance means essentially that you cannot predict the outcome of a particular event. For example, you cannot predict whether your next child will be a son or a daughter, even though you can specify the probability or likelihood. “Chance” does not mean lack of purpose or goal in science. If it did, we could say that absolutely everything in the natural world is by chance because we don’t see any purpose or goal in storms, in ocean currents, or anything else. Evolution certainly does involve randomness; it does involve unpredictable chance. For example, the origin of new genetic variation