'maintain a proposition' is correct and usable in written English.
You can use this expression when you are discussing the holding of an opinion or an argument, often in the context of an intellectual debate. For example: "My opponent and I both maintained our propositions throughout the debate, but neither of us could come to an agreement."
(Avramides' discussion here is confusing because she first responds to a case, due to Harman, of a person maintaining a proposition in full knowledge that no one will believe him, with the words, 'I think that in Harman's case the speaker is not really speaking to an audience at all' (p. 64).
This takes some of the lengthy and mentally taxing aspects of a job out of a worker's hands and into his sights, essentially "augmenting" the output of the workers themselves (which, of course, is the only way to maintain a value proposition to businesses and industries).
In order to maintain a similar value proposition to the 80GB/Spiderman 3 bundle, I expect to see a storage increase to 120 or 160GB at the same price point, plus the new Dual-Shock 3 controller.
For one thing, at some point even in what he takes to be the best solution one must maintain a strongly counter-intuitive proposition, which can only be justified when one sees that every other solution involves propositions that are even more counter-intuitive.
Understanding how to maintain a healthy state of the water cycle has become an important proposition for sustainable development of human society.
A lot of people don't have the stomach for full-blown S&M and it also requires not only the ability to maintain an erection (an increasingly dubious proposition in these perilous times) but also the ability to sustain a role--something which is incidentally one of the most important aspects of the actor's art.
Suppose Clifford is abducted by very powerful and very smart extraterrestrials, which offer him a single chance of salvation for humankind that he acquire and maintain belief in a proposition that lacks adequate evidential support, otherwise the destruction of humankind will result.
It's obvious that Clifford would do no wrong by swallowing the pills and bringing about a belief lacking adequate evidential support.[6] Moreover, since one is never irrational in doing one's moral duty, not only would Clifford not be immoral, he would not even be irrational in bringing about and maintaining belief in a proposition lacking adequate evidential support.
Enjoying a high-definition television and maintaining a "green" lifestyle are not mutually exclusive propositions.
Confronted with puzzles like Travis's about what it takes to be literally "at home," the literalist needs to maintain that the proposition I succeed in communicating by uttering a sentence often differs from the one my sentence expresses relative to prevailing values for relevant situating parameters, even when I speak with every surface sign of candor and directness.
