rugged. Furthermore, the bud at its rising has a certain appearance, but has a dissimilar appearance when in mid-heaven, and the same body one appearance in a wood and another in open country. The image again varies according to the position of the object, and a dove's neck according to the way it is turned. Since, then, it is not possible to observe these things apart from places and positions, their real nature is unknowable. The eighth mode is concerned with quantities and qualities of things, say heat or cold, swiftness or slowness, colourlessness or variety of colours. Thus wine taken in moderation strengthens the bodv, but too much of it is weakening ; and so with food and other things. The ninth mode has to do with perpetuity, strangeness, or rarity. Thus earthquakes are no surprise to those among whom they constantly take place ; nor is the sun, for it is seen every day. a This ninth mode is put eighth by Favorinus and tenth by Sextus and Aenesidemus ; moreover the tenth is put eighth by Sextus and ninth by Favorinus The tenth mode rests on inter-relation, e.g. between light and heavy, strong and weak, greater and less, up and down. Thus that which is on the right is not so by nature, but is so understood in virtue of its position with respect to something else ; for, if that change its position, the thing is no longer on the right. Similarly father and brother are relative terms, day is relative to the sun, and all things relative to our mind. Thus relative terms are in and by themselves unknowable. These, then, are the ten modes of perplexity.