Many individuals claim that Piaget's theory of cognitive development is empirically false or substantially disconfirmed by empirical research. Although there is substance to such a claim, any such conclusion must address three increasingly problematic issues about the possibility of providing an empirical test of Piaget's genetic epistemology: (1) the empirical underdetermination of theory by empirical evidence, (2) the empirical difficulty of testing competence-type explanations, and (3) the difficulty of empirically testing epistemic norms. This is especially true of a central epistemic construct in Piaget's theory — the epistemic subject. To illustrate how similar problems of empirical testability arise in the physical sciences, I briefly examine the case of Galileo and the correlative difficulty of empirically testing Galileo's laws. I then point out some important epistemological similarities between Galileo and Piaget together with correlative changes needed in science studies methodology. I conclude that many psychologists and science educators have failed to appreciate the difficulty of falsifying Piaget's theory because they have tacitly adopted a philosophy of science at odds with the paradigm-case of Galileo.