Siris has a nice short post on the use of “truth” in discourse:
This appeal to truth is incantatory: it is not an argument but a rhetorical ploy that usually involves a false dichotomy. By ritually displaying one’s ‘interest in the truth’ in contrast with someone else’s interest in something else, one simultaneously paints oneself as in possession of the truth and the other person as compromising the truth in favor of something else; when, of course, it is entirely possible that their concern with whatever it may be is itself a form of interest in the truth. Certainly, nothing says that you can’t simultaneously be interested in the truth and interested in other good things as well; and there is no reason to think that truth excludes every other good thing there may be.
It is also ironic, in that someone who appeals to truth this way is usually showing that they do, in fact, have other interests; one of which is to be superior to their opponents when it comes to the reputation for the truth.
It has always seemed to me that those interested in truth, as opposed to those who Pharisaically merely give it lip-service to win battles, are either metaphysicians or theologians, and the latter are interested solely for the purpose of claiming that they have it (and nobody else does, which leads back to Siris’ point above). Metaphysicians, who are so insane as a rule they should never be allowed to own a credit card (I’m joking, guys!), tend to focus on what Truth actually is or could be, rather than use the notion to make claims of Truth for this or that proposition. For myself, I emerged battered and charred from studying the question of truth as a pragmatist. If it works (for values of “work” that need volumes of explication), it’s true; or as I like to say, “it’s true enough for government work”.
Science isn’t about Truth, but rather it is about confirmation, reliability, testing, elimination, and other Bayes-like activities that scientists regularly undertake. They do not say “This theory is the ultimate truth” but “This theory has convinced enough of us who work in this field for the following reasons”, which they then list in enormous detail. If you want to know about the world, it seems that Truth is dispensable, and truth (small initial) will suffice.
So when people say something like “contagion [or whatever] theory is not true” they mean “I can find epistemic holes through which to drive my personal controversy”, as if that is a fault in science. It is actually science’s greatest virtue – that it doesn’t seek truth, but good theories.