 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 functioning of the senses, the balance of opposites in the healthy body, the immortality of the soul). In this sense he was dealing largely with what is “not perceptible” (aphanes). Alcmaeon is decidedly not an extreme skeptic, however, in that he is willing to assign clear understanding about such things to the gods and by implication admits that even humans have clear understanding of what is directly perceptible. Moreover, while humans cannot attain clarity about what cannot be perceived, Alcmaeon thinks that they can make reasonable judgments from the signs that are presented to them by sensation (tekmairesthai). He thus takes the stance of the scientist who draws inferences from what can be perceived, and he implicitly rejects the claims of those who base their account of the world on the certainty of a divine revelation (e.g., Pythagoras, Parmenides B1).