Dawkins famously and funniously (of course it’s not a word) objected to the Fourth Way by saying that the premises of the proof, if true, would commit us to the ridiculous idea of something maximally stinky. The first few times I heard the idea, I appealed to the standard responses: 1.) the measure of a privation is not a maximal privation; 2.) the proof is about transcendental perfections. But it strikes me now that what Dawkins is taking as a reductio ad absurdum is in fact an instance of exactly the principle Aquinas is appealing to in the Fourth Way.
There actually are very large R+D departments full of people who deal with stinkiness (deodorants, air fresheners, scented detergents, kitty litter, pet scent neutralizers etc. are not made by chance.) The job is not all abstract theorizing: there is a good deal women in lab coats sticking their noses where they don’t want to go. So suppose you took the tour of such an R+D department and, in the Q&A at the end of the tour, you asked “so, what is the stinkiest thing of them all?” Suppose that the stink-tester said “Oh, there’s nothing that I’d call the stinkiest of all”, and then promptly ended the tour. How would you spontaneously understand what she said? It seems to me you’d think that she meant to tell you that for whatever reason the various smells aren’t comparable. Perhaps stinks are irreducibly distinct and stinky in its own way, perhaps some things smell worse on different days or in different circumstances, etc. But the governing principle at work in all this is something like if there is no maximal, then it’s because the various things are not comparable. (We should clarify that the sort of comparability is in terms of greater and less.) But this is where the whole matter gets very interesting, since it follows from modus tollens that If various things are comparable in terms of greater and less, then there is some maximal – which is exactly the first principle of Aquinas’s proof.