It is the object of the present work to show how philosophy became a positive science; to indicate by what methods the human mind was enabled to conquer its present modicum of certain knowledge. The boldest and the grandest speculations came first. Man needed the stimulus of some higher reward than that of merely tracing the laws of phenomena. Nothing but a solution of the mystery of the universe could content him. Astronomy was derived from astrology: chemistry from alchemy, and physiology from auguries. The position occupied by philosophy in the history of mankind is that of the great initiative to positive science. It was the forlorn hope of mankind, and though it perished in its efforts, it did not perish without having led the way to victory. Thales, who was born at Miletus, in Asia Minor, and flourished in 585 B.C., is justly considered the father of Greek speculation. The step he took was small but decisive. He opened the physiological inquiry into the constitution of the universe. Seeing around him constant transformations--birth and death, change of shape, of size, and of mode of being, he could not regard any one of these variable states of existence as existence itself. He therefore asked, What is the beginning of things? Finding that all things were nourished by moisture, he declared that moisture was the principle of everything. He was mistaken, of course, but he was the first man to furnish a formula from which to reason deductively. Anaximenes (550 B.C.) pursued the method of Thales, but he was not convinced of the truth of his master's doctrine. He thought that the air was the prime, universal element, from which all things were produced and into which all things were resolved. Diogenes of Apollonia adopted the idea of Anaximenes, but gave a deeper significance to it. The older thinker conceived the vital air as a kind of soul; the younger man conceived the soul as a kind of air--an invisible force, permeating and actuating everything. This attribution of intelligence to the primal power or matter was certainly a progress in speculation; but another line of thought was struck out by Anaximander of Miletus, who had been a friend of Thales. He was passionately addicted to mathematics, and a great many inventions are ascribed to him; among others, the sun-dial and the geographical map.