Materialism and atheism are complementary threats to morality, though not in such a
fundamental way. If materialism is true, the soul is not immortal, and if atheism is true,
there is no divine justice. Kant held that both immortality and a just proportion of
happiness to virtue are components of the moral idea of the highest good. Thus under the
assumption of materialism and/or atheism, the highest good cannot be realized and the
object of morality is unattainable.
Speculative reason can do no more than secure the logical possibility of freedom,
immortality and God. There is no contradiction in any of the concepts, because they pertain
to things in themselves, which are not subject to the conditions of experience. As the actions
of an empirical subject, my actions are determined by causal laws, but as transcendental
subject, they may be transcendentally free. As an object in time, I have a limited span of
life, but as transcendental object I am not determined in time at all. God can never be met
with in any experience, be invoked as a necessary condition for experience, or proved
to exist. But a most real being is at least minimally thinkable. In the case of freedom,
"morality does not, indeed, require that freedom should be understood, but only that it
should not contradict itself, and so should at least allow of being thought" (Bxxix).
The transcendental ideas of God and immortality are relatively easy to accommodate on
Kant's scheme, since their their objects (assuming they have objects) are transcendent. An
immortal soul and a most real being are objects may in some unknown way be conditions of
experience (of ourselves and of the world, respectively). But we need not be concerned to
establish any connection between these objects and the objects of experience.
On the other hand, the idea of freedom requires a connection to experience. The reason is