Page:Popular Science Monthly Volume 43.djvu/549

 rest of the army passes. When a stream is too rapid for such a bridge, they form a suspension bridge by hanging from a friendly branch, and when wafted across by a breeze, they firmly anchor on the opposite shore, thus allowing the rest to cross in safety, and swing over themselves when the others have all crossed.



E live in a material age. Old beliefs are being supplanted by what seem to be new truths. The student finds on every hand vast volumes of learning bequeathed to him by those who have labored before him; and he who plunges deeply into this onward-rushing tide of material truths is often startled to find there an undertow sucking away the spiritual foundation. Skeptics, in scorn of latter-day religion, refer to the middle ages as the ages of faith. Christians, half dismayed, ask themselves. Is mankind to be swallowed up in the abyss of materialism?

It is the purpose of this paper to discuss life from a strictly material standpoint, and afterward to show that belief in the material interpretation does not cut one off from belief in the spiritual.

My own ideas have been largely influenced by German thought. Those who have had the privilege of listening to the lectures of Prof. Carl Yoit in Munich will recognize in this paper many traces of his teaching. Through him I received instruction in the material view of life.

The idea of the world held by Aristotle was that all things were made up of certain elementary matter, qualified by four properties—hot, cold, wet, and dry. Matter, with the properties cold and dry, was earth; with cold and wet, water; with hot and wet, air; and with hot and dry, fire. Different bodies varied from each other as they contained different proportions of the properties. These properties could be driven off from matter—that is to say, were separable from matter. Thus, the alchemists of the middle ages thought if they could drive a certain property out of mercury, or put a new one into it, clearly they would produce gold.

In like manner these same principles came into use for the explanation of life. During life there was a property present which departed at death—a living principle, a "vital force."

Galen, who was born at Troy, and who died at Rome 200, 