The accurate statement about Modernists, in general, is that theirs wasn't a search for the single, unifying meaning, the single, capital 'Truth', but rather that human beings have a capacity of breaking old habits and developing new ways of seeing the world outside their skins. There is a notion that that writing, art, architecture, film, et al, can be used in unique ways to bring about new perceptions of the addressed world, new ideas about human experience, rather than finding the one unchanging Truth, the single metaphysical road sign.
Modernism operates, in a real and traceable sense, within the the concept of the Pluralistic Universe, addressed by William James. There are those, I believe, who've taken up the postmodern critique of a grand narrative's conceit that it can present a finalized, totalized, fixed accounting of how the world operates and use it to sneakily, very sneakily promote a kind of apolitical apathy that benefits the rich , the ambitious, the ones who want to get power and hold on to it. If our accounts of real life situations are mere reflexes we're prone to reveal as part of a constraining metaphorical system that has blinded us from the real estrangement from power, then there is no point, then , of attempting to change the way things are, the way things work. Resistance is futile.
Why bother? This is the sort of defeatist wallow an insidious force would love to see on election day: population's anger toward the System turns into cynicism, a short cut to defeatist, no-show results. A revolution is thwarted without a repressive blow being struck. There is truth out there, goes the assumption, but it's less about an absolute dogma about an underlining definition than it is about how the human personality comes to perceive and form a sense of place and belonging within it. The search for singular Truth was a vain task, noted by Eliot, Pound and others: at it's best expression, Modernism remains an invigorating vehicle , a keen investigative sense.
Postmodernism searches for fallacies, so called, but we're stuck with the old binary oppositions that deconstructionists find offensive: we cannot have a define able sense of what is false unless we give ourselves over to an idea of what it opposes, the truth, or truths, plural. By default, postmodernism continues the Modernist project for what is useful in our descriptions. An extension of Modernism, in other words.