Full Idea
To believe in justice in an unjust world, you have to believe in a place of perfect justice (heaven), a time for perfect justice (eternity), and a cause of perfect justice (God).
Gist of Idea
Belief in justice requires belief in a place for justice (heaven), a time (eternity), and a cause (God)
Source
report of Immanuel Kant (Critique of Practical Reason [1788], I.II.II.V) by PG - Db (ideas)
Book Reference
Kant,Immanuel: 'Critique of Practical Reason (Third edition)', ed/tr. Beck,Lewis White [Library of Liberal Arts 1993], p.139
A Reaction
Compare Boethius in Idea 5765. I can see that we might need to grasp the ideals of eternal justice in order to understand morality, but belief in their genuine possibility, or even actuality, doesn't seem to follow.
Related Idea
Idea 5765 The reward of the good is to become gods [Boethius]