 The first people to describe themselves as empiricists (empeirikoi) were a group of medical writers of the Hellenistic period. We know of these thinkers only indirectly, through the work of other ancient writers, in particular Galen of Pergamon (129–ca. 200 CE). As medical practitioners, their primary concerns were practical: finding the correct method of diagnosis and treatment. But in discussing these matters they put forward some general epistemological claims, developing the empiricist tendencies already found in the Hippocratic writings (sect. 3.1).  In particular, they set themselves in opposition to those whom they called “rationalists” (logikoi) or “dogmatists” (dogmatikoi). What set them apart was a refusal to posit causes beyond those that can be observed.