Self-interest is inherent in man. It cannot be seen; it can only be understood. Self-interest has two forms, which may be described as natural motive and deliberate motive; and the conflict between them may be seen in the discussion that goes on within us. But the discussion has its purpose too; and it can modify natural motive as well as desire. Natural motive precedes discussion; and it is not only an intelligent, but also a good, desire that can be associated with the idea of sacrifice.
There is a common law of life applicable to all animals, because there is no essential difference between them at any time; and their similarity of behaviour is due not to similarity of motive, but of nature.
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