When one begins to catalog all the differences between Anselm’s ontological argument and the ones given by contemporary philosophers, he is almost tempted to say that they are completely different arguments. Almost but not quite. The definitive element of the ontological argument remains constant: one concludes to being, that is, the first time one encounters a being that actually exists is as a conclusion. The ontological argument therefore either proves or presupposes that some thoughts are prior to being, and therefore that not every thought is necessarily dependent on being.
St. Thomas has very little to say about ontological arguments, but what he says makes far more sense when we see him as critiquing the idea that some thoughts are prior to being. We cannot say that the premises of the ontological argument presuppose any being, for then the argument would simply be a cosmological argument, concluding from the being of various creatures (effects) the existence of God (the cause). What then? We have either disengaged being and thought or we are claiming that “to be” or “being” does not first mean what actually exists. In either case thought is disengaged from being or real existence, which of course raises the problem of how we know when thought attains to it.
Seen from this angle, modern thought is simply a working out of the logic of the ontological argument. This shows us a fundamental logic of Descartes’s Meditations, where Descartes strives to attain to the actual world through an ontological argument. The very problem that Descartes is trying to solve is one that is implicit in the ontological argument itself.