The Science of Conjecture: Evidence and Probability Before Pascal

by James Franklin

In discussing Aristotle’s definition of “probable” in the Topics, Albert distinguishes two senses of the word. “The probable (on which the dialectical syllogism is based) is the likely. Likely is taken in two ways. Either things are likely in themselves, in that the predicate’s being in the subject is itself likely, because the predicate is not in the subject per se nor the subject in the predicate, nor both in both, nor does the predicate necessarily and essentially inhere in the subject, but it is taken as likely not from necessary causes but from signs. Or the inherence is necessary, but is only understood through signs; and this is the probable commonly understood, even though it is necessary in itself: for example that the sun is larger than the earth (because it looks the same size everywhere).”