Seems to be some form of "category mistake" which could be easy to address. There are different contexts in which we can reason about truth. For metaphysics a

Seems to be some form of "category mistake" which could be easy to address. There are different contexts in which we can reason about truth. For metaphysics and related philosophical activities it makes sense to doubt any form of truth. To improve a train schedule in a small country, there is little sense in doubting that time exists. Is your friend able to fathom these kinds of ideas?