This paper presents a discussion of William Hamilton's thesis of the relativity of knowledge and of its reception in nineteenth- and twentiethcentury French philosophy. Scholars usually claim that Kant's transcendental philosophy is the main target of Bergson's rejection of the relativity of knowledge. In contrast, Bergson's plea for ‘intuition' as absolute knowledge should be replaced within the context of the long-lasting debates between French spiritualists and the Hamiltonians about the relations of metaphysics with psychology. In the service of this discussion the author locates an important anticipation of Bergson's philosophy of intuition in the forgotten figure of Ludovic Carrau.