These four translated treatises constitute an important component of Galen's considerable oeuvre, signified by their incorporation into the core material of the medical training curriculum well into the second millennium. Like others of Galen's major works, they have a well-defined purpose which might be summarized as the systematic examination of the nature and causation of disease and related phenomena. Unlike many of his works, they are singularly devoid of ad hominem arguments and the often quite virulent abuse heaped upon those with opposing views. Indeed, a strikingly even-handed, if somewhat cursory, treatment is given to one particular theory, the anarmoi/poroi theory of Asclepiades and its subsequent developments, which is elsewhere shown to be a particular Galenic bête noire. These treatises are, however, disappointingly lacking in any detailed consideration of earlier and other views and are, as a consequence, a poor source of information on such views, unlike a number of other Galenic works. This is especially unfortunate with respect to nosology.

In summarizing the content of these works, three aspects of diseases and their symptoms are considered: definition, classification and causation. Based on the sequence of the argument, and on the relative space devoted to these three matters, the impression is that the first two, definition and classification, are primarily to be seen as instruments for the analysis of the third – causation. Nonetheless, all three are obviously independently important despite their close interrelationship.