In the first place, his peculiar system of subjective idealism, involving the idea that time is but a mental form to which there corresponds nothing in the sphere of noiimenal reality, serves to give a peculiar philosophical interpretation to every doctrine of cosmic evolution.
Liberty, he says, in a much wider sense than Kant, is man's fundamental characteristic. Human freedom acts in the phenomenal, not in an imaginary noiimenal sphere.
In his fully mature or critical position he held that the noiimenal world was inaccessible to the speculative reason, and yet that we are not altogether excluded from it, since the practical reason, i.e.
Our capacity for acting as moral agents, assures us of the existence of a noiimenal world wherein freedom, God and immortality have a real place.