The pure practical reason must also postulate the existence of God as
the necessary condition of the attainment of the _summum bonum_. As the
perfect good can only be promoted by accordance of the will with the
moral law, so also this _summum bonum_ is possible only through the
supremacy of an Infinite Being possessed of causality harmonising with
morality. But the postulate of the highest derived good (sometimes
denominated the best world) coincides with the postulate of a highest
original good, or of the existence of God.
We now perceive why the Greeks could never solve their problem of the
possibility of the _summum bonum_, because they made the freedom of the
human will the only and all-sufficient ground of happiness, imagining
there was no need for the existence of God for that end. Christianity
alone affords an idea of the _summum bonum_ which answers fully to the
requirement of practical reason. That idea is the Kingdom of God.
The holiness which the Christian law requires makes essential an
infinite progress. But just for that very reason it justifies in man the
hope of endless existence. And it is only from an Infinite Supreme
Being, morally perfect, holy, good, and with an omnipotent will, that we
can hope, by accord with His will, to attain the _summum bonum_, which
the moral law enjoins on us as our duty to seek ever to attain.
The moral law does not enjoin on us to render ourselves happy, but
instructs us how to become worthy of happiness. Morality must never be
regarded as a doctrine of happiness, or direction how to become happy,
its province being to inculcate the rational condition of happiness, not
the means of attaining it. God's design in creating the world is not
primarily the happiness of the rational beings in it, but the _summum
bonum_, which super-adds another condition to that desire of human
beings, namely, the condition of deserving such happiness. That is to
say, the morality of rational beings is a condition which alone includes
the rule by observing which they can hope to participate in happiness at
the hand of an all-wise Creator.
The highest happiness can only be conceived as possible under conditions
harmonising with the divine holiness. Thus they are right who make the
glory of God the chief end of creation. For beyond all else that can be
conceived, that glorifies God which is the most estimable thing in the
whole world, honour for His command and obedience to His law, when to
this is added His glorious design to crown so beauteous an order of
things with happiness corresponding.