Tractatus 6.43 does not say that the world can or does wax and wane, but only that if good or bad willing changes the world then it must do so in this way, by changing the limits of the world. And these limits change as a whole, not here and there. The waxing world does not increase in this place or that, so to speak, by the addition of this or that. We cannot say in logic that the world has this and this in it but not that. And we cannot say that this world is bigger than that one because this has such-and-such in it but that world does not. The reference here to the limits of the world calls to mind 5.61, in which Wittgenstein writes that, “Logic fills the world; the limits of the world are also its limits.” The limits of logic in the world of the happy are greater than those in the world of the unhappy.
What can this possibly mean? It seems to have to do with language. By 5.61 the world is the space of possibilities. To say in logic that the world does not contain this would be precisely to exclude a certain possibility. And this, Wittgenstein says, we cannot do. The world contains everything that can be said or thought. So an expanded world, the world of the happy, is one in which more can be thought. The possibilities are greater. For the person who lives eternally (which is not a matter of living endlessly), the possibilities are unlimited.
I am not sure how much this helps explain what Wittgenstein means, and of course he tells us later that his propositions are nonsense, so it is easy to despair of understanding. But I think it is worth going on a little before giving up. The idea of languages or logics of different size, or an idea of such things, is not very difficult to grasp. The builders’ language in the Philosophical Investigations, for instance, is small. It contains few words and recognizes few possibilities. A language like English, on the other hand, is much bigger and seems to contain endless possibilities. We can create new sentences using existing words and grammatical forms, but we can also introduce new words and new grammatical forms. Tractarian happiness, then, might mean using the entire language or being open to it, not closing oneself in a rigidly conservative region of the language. The mind of the happy is rich, open, and imaginative.