Page:Early Greek philosophy by John Burnet, 3rd edition, 1920.djvu/116

102 Now it ought to be obvious that this is no innovation. Of course the employment of the letter alpha to represent the units is derived from the conventional notation; but otherwise we are clearly in presence of something which belongs to the very earliest stage of the science. We also gather that the dots were supposed to represent pebbles (ψῆφοι), and this throws light on early methods of what we still call calculation.

48. That Aristotle refers to this seems clear, and is confirmed by the tradition that the great revelation made by Pythagoras to mankind was precisely a figure of this kind, the tetraktys, by which the Pythagoreans used to swear, and we have the authority of Speusippos for holding that the whole theory was Pythagorean. In later days there were many kinds of tetraktys, but the original one, that by which the Pythagoreans swore, was the "tetraktys of the dekad." It was a figure like this:

and represented the number ten as the triangle of four.