The proprietor of Beyond Necessity has a post on objective reality which is directed against some New Age mumbo-jumbo. One of the commenters remarks, "Your argument for the existence of objective reality sounds very much like the ontological argument for God, and about as plausible." Ed, the proprietor, responds, ". . . the argument in no way resembles the logical form of the ontological argument."
What I will now do is present a sound ontological argument for objective reality. In so doing I will show that both proprietor and commenter are wrong. The latter because the argument is plausible; the former because it is ontological in form.
Definition. An ontological argument from mere concepts (aus lauter Begriffen, in Kant's famous phrase) is a ratiocinative procedure whereby the being instantiated of a concept is proven by sheer analysis of the concept. It is thus an argument in which one attempts to infer the existence of X from the concept X. For example, the existence of God from the concept God; the existence of a golden mountain from the concept golden mountain; the existence of objective reality from the concept objective reality. Concepts are mental items by definition. So a sound ontological argument will take us from thought to (extramental) being, in a manner to please Parmenides.
To mention a concept I use italics. Thus a word in italics refers to a concept.
1. We have and understand the concept the (total) way things are. It doesn't matter how we acquired this concept. We have it and we understand it. The way things are includes every fact, every obtaining state of affairs. So the way things are is equivalent to the world in Wittgenstein's sense: "Die Welt ist die Gesamtheit der Tatsachen, nicht der Dinge." (Tractatus 1.1) It is also equivalent to objective reality.
2. Now let us entertain the possibility that nothing answers to the concept the way things are, that the concept is not instantiated. We are thus to entertain the possibility that there is the concept in our minds but nothing to which it applies. We can formulate this possibility using the proposition *There is no objective reality.* Call this proposition P.
3. Could P be true? If P is true, then P is true in objective reality: that is just what 'true' means. So if P is true, then it is true in objective reality that there is no objective reality. This is a contradiction. So we must conclude that If P is true, then P is false. And if P is false, then of course P is false. So, necessarily, P is false, which implies that its negation is not only true but necessarily true: it is necessarily true that there is objective reality. So by sheer analysis of the concept objective reality one can validly infer that there is objective reality. Here then is a case in which an ontological argument from mere concepts is sound.
4. Have I pulled a fast one? Not as far as I can see. I have merely analyzed the concept objective reality, teasing out an implication of the claim that the concept is not instantiated.
5. Response to the commenter. The commenter is right to appreciate that the above sort of reasoning is ontological and thus similar to the God proof found in Descartes' Meditation V and criticized famously by Kant. He is wrong, however, to think that the former reasoning is cogent if and only if the latter is.
6. Response to the proprietor. The proprietor is right, as against the commenter, when it comes to the cogency of the above sort of reasoning. But the commenter is wrong to fail to see that it is ontological reasoning in a clear sense of that term. It is a priori reasoning from thought to being, from concept to existence.
Companion post: Four Kinds of Ontological Argument