As so often in Galen, the polemical aim is of major importance for the formulation of the argument. The recurrent target is that group of thinkers who deny intelligence or purpose as an explanans, and omit it from their causal accounts. Here Galen lumps together: a variety of ancient Atomist theorists; the followers of the Hellenistic medical author Erasistratus; and those of the more recent Asclepiades of Bithynia. All are accused of giving accounts which omit intelligence in the relevant sense, relying entirely on either spontaneous motions of bodies or mechanistic explanations of biological processes to explain the formation and maintenance of the complex processes of the human body.