Final answer:
Adam Smith believed that while individuals usually act as rational actors pursuing self-interest, they also possess altruistic qualities that take pleasure in others' happiness.
Step-by-step explanation:
Adam Smith’s ideas are deeply rooted in the concept that individuals generally act as rational actors pursuing self-interest. However, it should be noted that simplifying human nature to pure self-interest would be an oversimplification. Smith elaborates in his book, The Theory of Moral Sentiments, indicating that while individuals may act out of self-interest, altruistic tendencies are also inherent in human nature, as evidenced by his observation of the inherent pleasure people find in the happiness of others.