Conversation so far:
What was Kant's political philosophy?
listed several conditions that he thought necessary for ending wars and creating a lasting peace.
They included a world of constitutional republics.
What were the conditions?
His classical republican theory was extended in the Science of Right, the first part of the Metaphysics of Morals (1797).

Question: What else did he believe?
Self-contained rewrite: In addition to his republican theory, what else did Immanuel Kant believe in?