The doctrine of prejudice has many variants since its default version is inconsistent: its application to itself refutes it. This is no serious impediment, since it is easy to eliminate inconsistency. It is also easy to reword it—as any theory—so as to dodge its inconsistency and the counterexamples to it, and there are many ways to do so. Since the doctrine was—it still is—taken for granted by most of its adherents, they varied its wording casually. It is interesting to see how it altered through the ages and what its current popular variants are. And of course, the right place to start with is the philosophy of Locke, whose influence throughout the Age of Reason was tremendous. There is an immense scholarly literature on his work and its influence—most of it irrelevant to the present study. My discussion of his work is brief, as it concerns only the doctrine of prejudice. Locke’s epigone Dr. Isaac Watts takes a much larger share of this chapter since he expressed the spirit of the age better and since he was tremendously influential. This chapter ends with an attempt to assess the doctrine in its current variant: it is part-and-parcel of current inductivism, scarcely ever given explicit expression, much less public discussion, yet it provides inductivism its air of cogency.