Orthodoxy in epistemology maintains that some sources of belief, e.g. perception and introspection, generate knowledge, while others, e.g. testimony and memory, preserve knowledge. An example from Jennifer Lackey—the Schoolteacher case—purports to show that testimony can generate knowledge. It is argued that Lackey’s case fails to subvert the orthodox view, for the case does not involve the generation of knowledge by testimony. A modified version of the case does. Lackey’s example illustrates the orthodox view; the revised case refutes it. The theoretical explanation of knowledge from testimony as information transmission explains how testimony transfers knowledge and why it can generate knowledge. It also reveals the real difference between the so-called “generative” and so-called “preservative” sources. The former extract information; the latter transmit information.