Fair enough. It’s a very pragmatic assumption. If I was a solipsist, I might not bother getting out of bed in the morning. Or. . . I might run down the streets with no clothes on just for hoots, because hey-- nobody’s watching.
But pragmatism and absolute truth are not the same thing. In accepting your axiom as intrinsically truthful, you take what might be described as a leap of faith.
The problem is that once someone makes that decision, they are unlikely to un-make it. Now, we have science that shows that nothing I perceive exists in the sense that I experience it. There’s no real flatness to a table-top, for example, exact in a mathematical sense-- this is true because there is in fact no continuous surface to anything, flat or otherwise, in physics.
How do we reconcile this situation, when we know, like 100% know, that something is true, just as I know my desk is flat, and then we find out that what we knew does not represent a literal fact?
The scientific response is to keep bending the definition of material. “Oh yeah, sure we knew that everything was made of little balls, but now we know everything is really a complex superposition of quantum states.”
But I propose the opposite should occur. We should arrive at the conclusion that our axioms aren’t sound. They are pragmatic in the sense that they let us go to work and act with purpose, but they cannot represent Truth-As-It-Really_Is™ .