Unfortunately, the scientific method requires us to not take any empirical claim has guaranteed true - even (perhaps especially!?) the ones we are most sure of.
It requires us to take lots of empirical claims as true.
I agree - in order to advance we have to assume certain previous things are true. The use of the word 'guaranteed' was meant to emphatically emphasise that we must be aware of what those assumptions are, and be willing to test, challenge and revise those assumptions.
Is invoking an exchange of virtual gravitons really any better of a why than invoking a gravitational field described by an inverse square law?
Perhaps it is indeed the limitations of linguistics that has led us to encounter things such as "an exchange of virtual gravitons" in the literature. Whose ghostly cloaking cape does that Masked Higgs Boson wear anyway?
Silly me and here I was, thinking that the "Why" was to be sort of left off to the side of the road for now, in favor of a completing a more thorough description of the "What" and "How".