Epeidê to men aisthanesthai te kai kineisthai kata 1 proairesin idia tôn zôôn esti, to d' auxanesthai te kai trephesthai koina kai tois phytois, eiê an ta men protera tês psychês, ta de deutera tês physeôs erga. ei de tis kai tois phytois psychês metadidôsi kai diairoumenos autas onomazei phytikên men tautên, aisthêtikên de tên heteran, legei men oud' houtos alla, tê lexei d' ou pany tê synêthei kechrêtai. all' hêmeis ge megistên lexeôs aretên saphêneian einai pepeismenoi kai tautên eidotes || hyp' oudenos houtôs hôs hypo tôn 2 asynêthôn onomatôn diaphtheiromenên, hôs tois pollois ethos, houtôs onomazontes hypo men psychês th' hama kai physeôs ta zôa dioikeisthai phamen, hypo de physeôs monês ta phyta kai to g' auxanesthai te kai trephesthai physeôs erga phamen, ou psychês. II Thus we shall enquire, in the course of this treatise, from what _faculties_ these effects themselves, as well as any other effects of nature which there may be, take their origin. First, however, we must distinguish and explain clearly the various terms which we are going to use in this treatise, and to what things we apply them; and this will prove to be not merely an explanation of terms but at the same time a demonstration of the effects of nature. When, therefore, such and such a body undergoes no change from its existing state, we say that it is _at rest_; but, if it departs from this in any respect we then say that in this respect it _undergoes motion_.[9] Accordingly, when it departs in various ways from its pre-existing state, it will be said to undergo various kinds of motion. Thus, if that which is white becomes black, or what is black becomes white, it undergoes motion in respect to _colour_; or if what was previously sweet now becomes bitter, or, conversely, from being bitter now becomes sweet, it will be said to undergo motion in respect to _flavour_; to both of these instances, as well as to those previously mentioned, we shall apply the term _qualitative motion_. And further, it is not only things which are altered in regard to colour and flavour which, we say, undergo motion; when a warm thing becomes cold, and a cold warm, here, too we speak of its undergoing motion; similarly also when anything moist becomes dry, or dry moist. Now, the common term which we apply to all these cases is _alteration_. This is one kind of motion. But there is another kind which occurs in bodies which change their position, or as we say, pass from one place to another; the name of this is _transference_.[10] These two kinds of motion, then, are simple and primary, while compounded from them we have _growth_ and _decay_,[11] as when a small thing becomes bigger, or a big thing smaller, each retaining at the same time its particular form. And two other kinds of motion are _genesis_ and _destruction_,[12] genesis being a coming into existence,[13] and destruction being the opposite.