And, so, it was the Greeks, who first came to grips with the slippery surfaces of existence, at least, in any formal way. They were curious, as are all healthy men; and, it is curiosity which leads men to seek out the obverse of any question:

"Every fact is related on one side to sensation, and, on the other, to morals. The game of thought is, on the appearance of one of these two sides, to find the other: given the upper, to find the under side. Nothing so thin, but has these two faces, and, when the observer has seen the obverse, he turns it over to see the reverse. Life is a pitching of this penny, - heads or tails. We never tire of the game, because there is still a slight shudder of astonishment at the exhibition of the other face, at the contrast of the two faces. A man is flushed with success, and bethinks himself what this good luck signifies. He drives his bargain in the street, but it occurs, that he also is bought and sold. He sees the beauty of a human face, and searches the cause of that beauty, which must be more beautiful. He builds his fortunes, maintains the laws, cherishes his children, but he asks himself, why? and whereto? This head and this tail are called, in the language of philosophy, Infinite and Finite; Relative and Absolute; Apparent and Real; and many fine names beside. Each man is born with a predisposition to one or the other of these sides of nature, and it will easily happen that men will be found devoted to one or the other. One class has the perception of Difference, and is conversant with facts and surfaces; cities and persons; and the bringing certain things to pass; the men of talent and action. Another class have the perception of Identity, and are men of faith and philosophy, men of genius." [Ralph Waldo Emerson (1803-82)].7