Such skepticism about human knowledge is characteristic of one strand of early Greek thought. Both Alcmaeon’s predecessors (e.g., Xenophanes B34) and his successors (e.g., Philolaus B6) made similar contrasts between divine and human knowledge, but in Alcmaeon’s case, as in these other cases, we do not have enough evidence to be sure what he intended. Most of the subjects that Alcmaeon went on to discuss in his book could not be settled by a direct appeal to sense perception (e.g., the functioni