transient mist, before the preaching of the prophets of the ages to come, who, like the prophets of the ages that are long gone by, will speak only “as the Spirit gives them utterance.” LECTURE V. CHRISTIANITY AND GREEK PHILOSOPHY. The power of generalizing and of forming abstract ideas exists, or at least is exercised, in varying degrees among different races and at different times. The peculiar feature of the intellectual history of the Greeks is the rapidity with which the power was developed, and the strength of the grasp which it had upon them. The elaboration of one class of such ideas, those of form and quantity, led to the formation of a group of sciences, the mathematical sciences, which hold a permanent place. The earliest and most typical of these sciences is geometry. In it, the attention is drawn away from all the other characteristics of material things, and fixed upon the single characteristic of their form. The forms are regarded in themselves. The process of abstraction or analysis reaches its limit in the point, and from that limit the mind, making a new departure, begins the process of construction or synthesis. Complex ideas are formed by the addition of one simple idea to another, and having been so formed can be precisely defined. Their constituent elements can be distinctly stated, and a clear boundary drawn round the whole. They can be so marked off from other ideas that the idea which one man has formed can be communicated to and represented in another man’s mind. The inferences which, assuming certain “axioms” to be true and certain “postulates” to be granted, are made by one man, are accepted by another man or at once disproved. There is no question of mere probability, nor any halting between two opinions. The inferences are not only true but certain. The result is, that there are not two sciences of geometry, but one: all who study it are agreed as to both its definitions and its inferences.