All the other proofs of God are weak or worthless beside this one. The existence of God has been deduced from the idea of God: if we have the idea of God, it is necessary that He should exist. A weak proof, for we can have an idea which does not correspond with an object. The existence of God has been deduced from the idea of causality; for all that is, a cause is necessary, this cause is God. A weak proof, for things being as they are, there is necessity for ... cause; but a cause and a _single_ cause, why? There could be a series of causes to infinity and thus the cause of the world could be the world itself. The existence of God has been deduced from the idea of design well carried out. The composition, the ordering of this world is admired; this world is well made; it is like a clock. The clock supposes a clock-maker; the fine composition of the world supposes an intelligence which conceived a work to be made and which made it. Perhaps; but this consideration only leads to the idea of a manipulation of matter, of a demiurge, as the Greeks said, of an architect, but not to the idea of a _Creator;_ it may even lead only to the idea of several architects and the Greeks perfectly possessed the idea of a fine artistic order existing in the world when they believed in a great number of deities. This proof also is therefore weak, although Kant always treats it with respect. The sole convincing proof is the existence of the moral law in the heart of man. For the moral law to be accomplished, for it not to be merely a tyrant over man, for it to be realised in all its fullness, weighing on man here but rewarding him infinitely elsewhere, which means there is justice in all that, it is necessary that somewhere there should be an absolute realizer of justice. God must exist for the world to be moral. Why is it necessary for the world to be moral? Because an immoral world with even a single moral being in it would be a very strange thing. Thus, whilst the majority of philosophers deduced human liberty from God, and the spirituality of the soul from human liberty, the immortality of the soul from human spirituality, and morality from human immortality, Kant starts from morality as from the incontestable fact, and from morality deduces liberty, and from liberty spirituality, and God from the immortality of the soul with the consequent realization of justice. He has effected an extraordinarily powerful reversal of the argument generally employed.