In the course of this book I shall be concerned to prove that the fundamental concept in social science is Power, in the same sense in which Energy is the fundamental concept in physics. Like energy, power has many forms, such as wealth, armaments, ,civil authority, influence on opinion. No one of these can be regarded as subordinate to any other, and there is no one form from which the others are derivative. The attempt to treat one form of power, say wealth, in isolation, can only be partially successful, just as the study of one form of energy will be defective at certain points, unless other forms are taken into account.
Source: Power, 1938.
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