I have endeavoured in this treatise to show that the Principle of Sufficient Reason is a common expression for four completely different relations, each of which is founded upon a particular law given _à priori_ (the principle of sufficient reason being a synthetical _à priori_ principle). Now, according to the principle of _homogeneity_, we are compelled to assume that these four laws, discovered according to the principle of specification, as they agree in being expressed by one and the same term, must necessarily spring from one and the same original quality of our whole cognitive faculty as their common root, which we should accordingly have to look upon as the innermost germ of all dependence, relativeness, instability and limitation of the objects of our consciousness--itself limited to Sensibility, Understanding, Reason, Subject and Object--or of that world, which the divine Plato repeatedly degrades to the ἀεὶ γιγνόμενον μὲν καὶ ἀπολλύμενον, ὄντως δὲ οὐδέποτε ὄν (ever arising and perishing, but in fact never existing), the knowledge of which is merely a δόξα μετ' αἰσθήσεως ἀλόγου, and which Christendom, with a correct instinct, calls _temporal_, after that form of our principle (Time) which I have defined as its simplest schema and the prototype of all limitation. The general meaning of the Principle of Sufficient Reason may, in the main, be brought back to this: that every thing existing no matter when or where, exists _by reason of something else_. Now, the Principle of Sufficient Reason is nevertheless _à priori_ in all its forms: that is, it has its root in our intellect, therefore it must not be applied to the totality of existent things, the Universe, including that intellect in which it presents itself. For a world like this, which presents itself in virtue of _à priori_ forms, is just on that account mere phenomenon; consequently that which holds good with reference to it as the result of these forms, cannot be applied to the world itself, _i.e._ to the thing in itself, representing itself in that world. Therefore we cannot say, "the world and all things in it exist by reason of something else;" and this proposition is precisely the Cosmological Proof.