=146.= The Stoics fancifully derive the word αἴσθησις (‘sensation’) from εἴσθεσις (‘storage’); it is therefore, strictly speaking, the process by which the mind is stored[16]; but it is also, from an opposite point of view, the process by which the mind reaches out towards an external object[17]. From the object (αἰσθητόν) proceed waves which strike upon the sense-organ (αἰσθητήριον); this impact is called a ‘sensation’ in a narrower sense. At the same time there proceeds from the mind (which is the ruling part or ‘principate’ of the soul), a ‘spirit’ or thrill which goes out to meet this impact; and this spirit and its operation are also called ‘sensation[18].’ As a result of the contact of these two waves, and simultaneously with it, there is produced in the soul an effect like the imprint of a seal[19], and this imprint is the φαντασία or ‘mind-picture.’ That the process may be sound, it is necessary that the intellect be in a healthy state, and further that the organ of sense be healthy, the object really there, and the place and the manner in accord[20]. But we must carefully distinguish between the single sensation and the mind-picture. A flash of light, a cry, a touch, a smell, a thrill of pleasure or pain, is always that which the senses declare it to be[21]; here there is no possibility of error; so understood ‘the sensations are always true[22].’ But if we go in each case a step further; if we say ‘that is white,’ ‘this is sweet,’ ‘this is musical,’ ‘this is fragrant,’ ‘that is rough,’ we are now dealing with mind-pictures, not with ‘sensations’ in the strict sense[23]. And as to the mind-pictures we agree with the Academics that things are not always what they seem; ‘of the mind-pictures some are true, some are false[24].’ [Sidenote: The criterion of clearness.]