
If you cannot fathom or see the sensibility in the beliefs of another, then the failure is almost certainly in your understanding, not in their intelligence or reason. More often than not, people have logical and coherent reasons for believing what they believe. More often than not, your difference in view simply comes down to them having underlying presumptions that are different from your own. But if you did share their presumptions, more often than not you might very well come to the same conclusions as them.
It is maturity to seek first what those presumptions are, to see the reason and logic that follows from them, and to appreciate that your brother or sister is an intelligent being trying to do their best with what they have, just like you.
Furthermore, in many cases those presumptions are both unprovable and unfalsifiable. Thus, your brother or sister may indeed be wrong, and the conclusions drawn from them wrong as well, but you’ll never be able to demonstrate it by logical argument.
Most arguments around differences in belief are therefore a complete waste of energy. Most debaters will never extend the grace of acknowledging the reasonability in other’s conclusions given their background, nor address the actual presumptions on which everything depends. Instead, people tend to argue on a surface layer for positions that the other cannot accept, and no meaningful change occurs.

