The student of history knows well that the Greeks made great progress in the science of mechanics as well as of geometry. At first sight, it appears strange that with this advance in mechanics so little advance was made in the direction of modern science. The seeming paradox impels us to ask why it was that mechanics remained a separate science, why it was not used in description and explanation of natural phenomena after the manner of Galileo and Newton. The answer is found in the social parallelism already mentioned. Socially speaking, machines, tools, were devices employed by artisans. The science of mechanics had to do with the kind of things employed by human mechanics, and mechanics were base fellows. They were at the lower end of the social scale, and how could light on the heavens, the highest, be derived from them? The application of considerations of mechanics to natural phenomena would moreover have implied an interest in the practical control and utilization of phenomena which was totally incompatible with the importance attached to final causes as fixed determiners of nature. All the scientific reformers of the sixteenth and seventeenth centuries strikingly agree in regarding the doctrine of final causes as _the_ cause of the failure of science. Why? Because this doctrine taught that the processes of nature are held in bondage to certain fixed ends which they must tend to realize. Nature was kept in leading strings; it was cramped down to production of a limited number of stereotyped results. Only a comparatively small number of things could be brought into being, and these few must be similar to the ends which similar cycles of change had effected in the past. The scope of inquiry and understanding was limited to the narrow round of processes eventuating in the fixed ends which the observed world offered to view. At best, invention and production of new results by use of machines and tools must be restricted to articles of transient dignity and bodily, not intellectual, use. When the rigid clamp of fixed ends was taken off from nature, observation and imagination were emancipated, and experimental control for scientific and practical purposes enormously stimulated. Because natural processes were no longer restricted to a fixed number of immovable ends or results, anything might conceivably happen. It was only a question of what elements could be brought into juxtaposition so that they would work upon one another. Immediately, mechanics ceased to be a separate science and became an organ for attacking nature. The mechanics of the lever, wheel, pulley and inclined plane told accurately what happens when things in space are used to move one another during definite periods of time. The whole of nature became a scene of pushes and pulls, of cogs and levers, of motions of parts or elements to which the formulae of movements produced by well-known machines were directly applicable.