Primitive man is almost as material in his thinking as is the young child.  Of this we have traces in many of the words which have come to be applied to the mind.  Our word “spirit” is from the Latin spiritus, originally a breeze.  The Latin word for the soul, the word used by the great philosophers all through the Middle Ages, anima (Greek, anemos), has the same significance.  In the Greek New Testament, the word used for spirit (pneuma) carries a similar suggestion.  When we are told in the Book of Genesis that “man became a living soul,” we may read the word literally “a breath.”

What more natural than that the man who is just awakening to a consciousness of that elusive entity the mind should confuse it with that breath which is the most striking outward and visible sign that distinguishes a living man from a dead one?

That those who first tried to give some scientific account of the soul or mind conceived it as a material thing, and that it was sufficiently common to identify it with the breath, we know from direct evidence.  A glance at the Greek philosophy, to which we owe so much that is of value in our intellectual life, is sufficient to disclose how difficult it was for thinking men to attain to a higher conception.

Thus, Anaximenes of Miletus, who lived in the sixth century before Christ, says that “our soul, which is air, rules us.”  A little later, Heraclitus, a man much admired for the depth of his reflections, maintains that the soul is a fiery vapor, evidently identifying it with the warm breath of the living creature.  In the fifth century, B.C., Anaxagoras, who accounts for the ordering of the elements into a system of things by referring to the activity of Mind or Reason, calls mind “the finest of things,” and it seems clear that he did not conceive of it as very different in nature from the other elements which enter into the constitution of the world.

Democritus of Abdera (between 460 and 360 B.C.), that great investigator of nature and brilliant writer, developed a materialistic doctrine that admits the existence of nothing save atoms and empty space.  He conceived the soul to consist of fine, smooth, round atoms, which are also atoms of fire.  These atoms are distributed through the whole body, but function differently in different places—­in the brain they give us thought, in the heart, anger, and in the liver, desire.  Life lasts just so long as we breathe in and breathe out such atoms.

The doctrine of Democritus was taken up by Epicurus, who founded his school three hundred years before Christ—­a school which lived and prospered for a very long time.  Those who are interested in seeing how a materialistic psychology can be carried out in detail by an ingenious mind should read the curious account of the mind presented in his great poem, “On Nature,” by the Roman poet Lucretius, an ardent Epicurean, who wrote in the first century B.C.