 When we inquire into the way ancient authors have used the information provided by Aëtius’ Placita, by its progeny, and by its post-Theophrastean predecessors, we often find that the function of these collections of doxai is not much different from the functions of similar overviews in the context of Aristotle’s dialectical discussions. The main objective of these authors, who are in a position to base themselves on evidence that has already been provided with a definite structure, is to ascertain whether a given doxa may eventually prove to be useful, and which doxai should be rejected—depending, naturally, on the point of view of the user (who may be a physician or a philosopher, a Stoic or an Epicurean, a Platonist or an Aristotelian, a pagan or a Christian). Sometimes all the doxai belonging to a specific sub-set, or dealing with a specific theme, may turn out to be unacceptable, or useless, under certain circumstances or to somebody in particular. The fact should never be lost from view that the Placita merely provides a status quaestionis: material for instruction, discussion and reflection on, say, the shape of the moon, or the size of the sun, or the causes of earthquakes, or of the flooding of the Nile, or the various explanations of visual perception. Neither a suspension of judgement, in the manner of the Skeptics, nor a positive outcome, in the manner of Aristotle or the Stoics, is ever formulated, no explicit advice ever given either way. Only very rarely is there a critical note.