Such is, summarily stated, the substance of their logical teaching. And in order to give it also in detail, let. me now cite as much of it as comes within the scope of their introductory handbook. I will quote verbatim what Diocles the Magnesian says in his Synopsis of Philosophers. These are his words : " The Stoics agree to put in the forefront the doctrine of presentation and sensation, inasmuch as the standard by which the truth of things is tested is generically a presentation, and again the theory of assent and that of apprehension and thought, which precedes all the rest, cannot be stated apart from presentation. For presentation comes first ; then thought, which is capable of expressing itself, puts into the form of a proposition that which the subject receives from a presentation." There is a difference between the process and the outcome of presentation. The latter is a semblance in the mind such as may occur in sleep, while the former is the act of imprinting something on the soul, that is a process of change, as is set forth by Chrysippus in the second book of his treatise Of the Soul (De animd). For, says he, we must not take " impression " in the literal sense of the stamp of a seal, because it is impossible to suppose that a number of such impressions should be in one and the same spot at one and the same time. The presentation meant is that which comes from a real object, agrees with that object, and has been stamped, imprinted, and pressed seal-fashion on the soul, as Mould not be the case if it came from an unreal object. According to them some presentations are data of