Abstract
The author examines the sting inherent in the title of Kant’s work on the Unique possible foundation of a demonstration of the existence of God, published in 1762. In this work, Kant admits not wanting to establish a formal demonstration of the existence of God, but only the foundations of such a demonstration. In this way, he develops less than a proof, but at the same time more, i.e. the unique possible foundation of such a proof. The author critically analyses that in this formula, obviously to a different extent, both the leibnizian proof starting from the possibles and the wolffian, so-called a posteriori proof, at a critical moment of their respective articulations, resort to a second argumentation in order to prove the existence of the necessary being and that they are thus not auto-sufficient (unique).