Date of this Version
Metaphysik Vigilantius (K3), 29:1020 (1794/95)
One well-known point of emphasis in the critical philosophy is that only transcendental idealism can safeguard the possibility of the spontaneity and agent-causal freedom of rational beings. If such freedom were not possible, then in Kant’s estimation there would be no hope for conceiving of rational agents as morally responsible; for if rational agents were totally in the grip of the deterministic causal nexus of the Spatio-temporal world then moral requirements could not apply.
However, as the epigraph above makes clear, Kant also considers the causal nexus of phenomenal nature to threaten the status of human beings not just as moral agents but even as "intelligence"- that is, as beings capable of being determined in their acts by their intellectual faculties. Phenomenal causes, if they were the only possible causes upon which action was based, would threaten the very possibility of our status as rational beings. Hence, according to Kant, the rational acts of rational agetns depend for their generation on an intellectual faculty whose acts are independent of the phenomenal causal nexus.