It is actually a nice question how far Descartes himself endorses the monological and metaphysically dualistic theory of mind associated with his name and his legacy in early modern philosophy. But Fichte does reject this tradition, by suggesting that an immaterial thinking substance is an incoherent notion, and a rational being whose rationality was not developed through communication with others is a transcendental impossibility.
Allen W. WoodKant was a rational theologian. He did not pretend to be a biblical or revealed theologian.
Allen W. WoodI don't think Kant's theory looks bad to people except insofar as they have misunderstood it (for instance, as heartless and ironheaded, or as committed to an absurd metaphysical conception of freedom that violates Kant's own philosophy).
Allen W. WoodWe can never prove that we are free or integrate our freedom in any way into our objective conception of the causal order of nature.
Allen W. Wood