To know an argument is true requires something humans simply don’t have: infallibility.
The brain is too fragile, the universe is too random, for a reasonable mind to accept anything as Absolute Truth.
However, that doesn’t mean there aren’t signposts that can point us toward better and more rational thoughts. Having the ability to discern the shades of gray is part of what makes me happy to be human.
Underestimation of this power leads us down dangerous paths. Always doubt your theories, but put them to the test by implementing them. You shouldn’t be absolutely convinced of what works, but you may be convinced of what doesn’t.
“I only look at backtested results to see what didn’t work. It can’t prove anything going forward.”