In this treatise, Schopenhauer argues that the foundation of ethics is compassion. This represents, in his view, the genuinely moral spring of human actions, the only one that differs from selfishness, which aims at the satisfaction of one's own desires, as well as from malice, which aims at the pain of others.

This ethics of compassion is contrasted with Kantian duty ethics, which Schopenhauer subjects to thorough criticism. Its ultimate foundation is the metaphysical position of the philosopher that all beings, despite their apparent differences, essentially identify with each other.

The treatise On the Foundation of Morality is among those "smaller" works of Schopenhauer that complement his main work (The World as Will and Representation), enriching and developing a specific theme that is presented more succinctly in the main work. Since it was intended to be submitted for a competition, it addresses its subject in a particularly accessible manner and without explicit reference to its metaphysical dimension. Thus, it constitutes one of the classic works on this issue, a timely and still relevant response to this always central philosophical question.