Rationality and Economics

Part of Spinoza's concept of Rational behavior is that it adequately promotes one's well-being.  Part of Kant's is that it promotes the happiness of others.  In contrast, the concept of Rational behavior that is a staple of modern Economic theory, though usually not explicitly formulated, seems to be Humean--the calculation of the best means to maximum personal pleasure and minimum personal pain.  Apparently validated by that concept are gaining where others lose, and purchasing a pet rock.  Now, the Prisoner's Dilemma exposes some of the inherent weaknesses in that concept, but regardless, it plainly diverges from both Spinoza's and Kant's.  For, according to the former, Pleasure is usually no more than a semi-Rational motivation, and according to the latter, profiting from the loss of another usually violates Rationality.  In other words, the concept of Rationality taken for granted in these theories, reflecting their origins in British Sentimentalism, is arbitrary.