This paper pursues the double task of (a) presenting Cassirer’s Philosophy of Symbolic Forms as a systematic critique of culture and (b) assessing this systematic approach with regards to the question of reason vs. relativism. First, it reconstructs the development of his theory to its mature presentation in his Philosophy of Symbolic Forms. Cassirer here presents a critique of culture as fulfilling Kant’s critical work by insisting on the plurality of reason as spirit, manifesting itself in symbolic forms. In the second part, the consequences of this approach will be drawn by considering the systematics Cassirer intended with this theory. As can be reconstructed from his metaphilosophical reflections, the strength of Cassirer’s philosophy is that it accounts for the plurality of rational-spiritual activity while at the same time not succumbing to a relativism. The Philosophy of Symbolic Forms steers a middle course between a rational fundamentalism and a postmodern relativism.