Recent scholarship has stressed that it is not useful to speak of Greek scientific experimentation in sweeping fashion. The Greeks did perform scientific experiments, but the quantity, quality, and areas explored varied over different periods. Thus, while at certain times such testing procedures flourished, at other times very few actual experi? ments were performed. So, too, certain fields were more fruitful or feasible for experimentation than others.1 Those who tend to play down the quantity and quality of Greek scientific experimentation usually point to the Greeks' preference for speculation and theory over obser? vation and performance of manual tasks.2 Thought experiments allow the mind to range freely without leaving one's armchair or getting one's hands dirty, and that may be why such mental tests were favored by Greek thinkers, from Xenophanes onward. My purpose here is to study two thought experiments found in the Dissoi Logoi in conjunction with several related trials found in Herodotus, Xenophon, Plato, and Xe? nophanes. All these thought experiments make use of hypothetical hu? man beings and deal with educational and ethical matters. Generally speaking, these hypothetical tests contrast two types of people, either individuals or larger groups, in an attempt to determine the roles played by heredity and environment in the acquisition of knowledge and moral values.