=149.= Close upon assent follows ‘comprehension’ (κατάληψις, _comprehensio_): this is the ratification of the assent given, the fixing irrevocably in the mind of the picture approved. This picture now becomes a ‘comprehension-picture’ (καταληπτικὴ φαντασία), and as such a unit of knowledge. We may understand thereby that the mind has grasped the external object[38], and this is the plain meaning of Zeno’s simile; or we may say that the object has gained a hold upon the mind, and has left its stamp upon it. Both interpretations are consistent with Stoic doctrine: but the former view, which represents the soul as active and masterful, undoubtedly expresses the more adequately the meaning of the school[39]. From this mutual grasp there follows an important physical deduction. Since only like can grasp like, the soul must be like the object, and the popular dualism of mind and matter is (to this extent) at an end[40]. Still this likeness is not complete; and the soul in sensation does not grasp the object from every point of view, but only so far as its own nature permits in each case[41]. For this reason the trained observer and the artist grasp far more of the object than the ordinary man[42]. [Sidenote: From sensation to reason.] =150.= The soul, having grasped single mind-pictures, retains its hold upon them by memory[43]; the frequent exercise of which keeps each picture fresh and complete[44]. As the air, when an orchestra is performing, receives the impression of many sounds at the same time, and yet retains the distinctive tone of each[45], so the soul by concurrent alterations of its texture preserves its hold on the separate pictures it has once grasped. Fresh operations of soul now supervene. First, from the comparison of many like pictures, comes ‘experience’ (ἐμπειρία, _experientia_)[46]; out of other comparisons, ‘similitude’ (ὁμοιότης), as ‘Socrates’ from his portrait; and ‘analogy’ (ἀναλογία, _proportio_), as ‘the centre of the earth’ from that of other spheres; ‘transference’ (μετάθεσις, _translatio_), as ‘eyes in the heart’; ‘composition’ (σύνθεσις, _compositio_), as ‘a Hippocentaur’; ‘opposition’ (ἐναντίωσις, _transitio_), as ‘death’ from life; ‘deprivation’ (κατὰ στέρησιν), as ‘a cripple[47].’ All these are based on the general principle of likeness and unlikeness, and may be summed up under the general heading of ‘reason’s work of comparison’ (_collatio rationis_)[48], or shortly, of reason (λόγος)[49]. Sensation shews us the present only; but reason brings the past and the future within our view, and points out to us the workings of cause and effect[50]. [Sidenote: Perceptions and Conceptions.]