With increase of knowledge, and along with the inquiry as to the nature of causes, there arose an inquiry also as to what reality was. What was the essential nature of the stuff of which the universe was made, what was matter, what were things in themselves, what were the noumena (the realities), lying back of the phenomena (the appearances)? Gradually ideas explaining motion, force, and energy were developed. At the same time inquiry was made as to the nature of man, the working of his mind, the nature of thought, the relation of his concepts (ideas) to his perceptions (knowledge gained through the sense) and the relations of both to the noumena (realities).]283 [The general direction taken by this inquiry has been that of a conflict between two schools of thought which we may characterize as those of absolutism and of relativism.]* [The ancient Greek philosophers believed that they could tap a source of knowledge pure and absolute by sitting down in a chair and reasoning about the nature of time and space, and the mechanism of the physical world.]221 [They maintained that the mind holds in its own right certain concepts than which nothing is more fundamental. They considered it proper to conceive of time and space and matter and the other things presented to their senses by the world as having a real existence in the mind, regardless of whether any external reality could be identified with the concept as ultimately put forth. They could even dispute with significance the qualities which were to be ascribed to this abstract conceptual time and space and matter. All this was done without reference to the external reality, often in defiance of that reality. The mind could picture the world as it ought to be; if the recalcitrant facts refused to fit into the picture, so much the worse for them. We all have heard the tale of how generation after generation of Greek philosophers disputed learnedly why and how it was that a live fish could be added to a brimming pail of water without raising the level of the fluid or increasing the weight; until one day some common person conceived the troublesome idea of trying it out experimentally to learn whether it were so--and found that it was not. True or false, the anecdote admirably illustrates the subordinate place which the externals held in the absolutist system of Greek thought.]*