The former distinguishes between ratio essendi and ratio cognoscendi, rejects the ontological argument, and defends determinism against Crusius on Leibnitzian grounds.

The modern equivalent of fatum is, as Guyau has said, determinism.

From the former he appropriates pantheism, from the latter optimism and the concept of individuality; he shares determinism with both: all events, even the decisions of the will, are subject to the law of necessity.