THE THEORY OF INTEREST

For each individual only those events which comewithin the purview of his experience are of direct con-cern. It is these events—the psychic experiences of theindividual mind—which constitute ultimate income forthat individual. The outside events have significancefor that individual only in so far as they are the meansto these inner events of the mind. The human nervoussystem is, like a radio, a great receiving instrument. Ourbrains serve to transform into the stream of our psychiclife those outside events, which happen to us and stimu-late our nervous system.

But the human body is not ordinarily regarded as anowned object, and only those events in consciousnesstraceable to owned objects other than the human bodyare generally admitted to be psychic income. However,the human machine still plays a role in so far as, throughits purposeful activities, it produces, or helps produce,other owned objects which are material sources of desir-able events—food, houses, tools, and other goods, whichin their turn set in motion a chain of operations whoseultimate effect is registered in our stream of conscious-ness. The important consideration from this point ofview is that human beings are ever striving to controlthe stream of their psychic life by appropriating and util-izing the materials and forces of Nature.

In Man’s early history he had little command over hisenvironment. He was largely at the mercy of naturalforces—wind and lightning, rain and snow, heat andcold. But today Man protects himself from these bymeans of those contrivances called houses, clothing, andfurnaces. He diverts the lightning by means of lightningrods. He increases his food supply by means of appropri-ated land, farm buildings, plows, and other implements.

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