ON LIFE-SATISFACTION.
THE purpose of this article is to discuss and prove the fol- lowing proposition : The degree of life -satisfaction of separate individuals or of whole societies is measured, not by the absolute quantity of goods possessed, but by the rapidity with which this quan- tity is increasing. In other words, the feeling of satisfaction or of self-contentment is a result or a function, not of the quantity of goods, but of the rapidity with which the quantity varies from time to time. Mathematically, this proposition may be expressed thus : Let the curve PQRST in the accompanying diagram represent the aggregate quantity of goods material, moral, and intellectual possessed at any given time by an indi- vidual, a human society, or a nation. This curve, which we may call the "progress curve," generally has an aspect like that shown in the diagram :
o-
II
A\
t = f jme
An organism or a society develops first very slowly and then with increasing rapidity ; hence the corresponding part, PQ, of the curve (early civilization) rises slantingly. In youth
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