It is a delight to discover the illuminating thoughts which came to the minds of these men; and, on the other hand, it is amusing to see how recklessly they launched themselves on boundless seas when they were unprovided with chart and compass. They were like brilliant children, who know little of the dangers of the great world, but are ready to undertake anything. These philosophers regarded all knowledge as their province, and did not despair of governing so great a realm. They were ready to explain the whole world and everything in it. Of course, this can only mean that they had little conception of how much there is to explain, and of what is meant by scientific explanation. It is characteristic of this series of philosophers that their attention was directed very largely upon the external world. It was natural that this should be so. Both in the history of the race and in that of the individual, we find that the attention is seized first by material things, and that it is long before a clear conception of the mind and of its knowledge is arrived at. Observation precedes reflection. When we come to think definitely about the mind, we are all apt to make use of notions which we have derived from our experience of external things. The very words we use to denote mental operations are in many instances taken from this outer realm. We "direct" the attention; we speak of "apprehension," of "conception," of "intuition." Our knowledge is "clear" or "obscure"; an oration is "brilliant"; an emotion is "sweet" or "bitter." What wonder that, as we read over the fragments that have come down to us from the Pre-Socratic philosophers, we should be struck by the fact that they sometimes leave out altogether and sometimes touch lightly upon a number of those things that we regard to-day as peculiarly within the province of the philosopher. They busied themselves with the world as they saw it, and certain things had hardly as yet come definitely within their horizon. 2. THE GREEK PHILOSOPHY AT ITS HEIGHT.--The next succeeding period sees certain classes of questions emerge into prominence which had attracted comparatively little attention from the men of an earlier day. Democritus of Abdera, to whom reference has been made above, belongs chronologically to this latter period, but his way of thinking makes us class him with the earlier philosophers. It was characteristic of these latter that they assumed rather naively that man can look upon the world and can know it, and can by thinking about it succeed in giving a reasonable account of it. That there may be a difference between the world as it really is and the world as it appears to man, and that it may be impossible for man to attain to a knowledge of the absolute truth of things, does not seem to have occurred to them.