Abstract: In his early work (1747-56), Kant is Leibnizian in his commitment to a distinction between things in themselves and phenomena, grounded on a contrast between intrinsic and relational properties. He is anti-Leibnizian in his argument that there is Receptivity, since there is real causal influence; and anti-Leibnizian in his argument that there is Irreducibility, since relations fail to supervene on intrinsic properties. The latter argument is of considerable interest, and open to interpretation: whether it moves illicitly from unilateral to bilateral reducibility; which notions of intrinsicness are appropriate; whether it concerns relations in general, or causal power (specifically attraction and impenetrability in a pioneering field theory). Irreducibility here yields a doctrine of superadded force: since ‘substance never has the power, through its own intrinsic properties, to determine others’, such power is added by God.

Keywords: causal power, field, force, intrinsic, irreducibility, Kant, Leibniz, reduction, relational, superaddition, supervenience,