[sclarisse]

> But if you don't trust other humans to decide or even know what the highest good is, why would you trust yourself. Aren't you just a human as well?

Because in practice other-humans deciding what is the “highest good” for you have a distressing tendency to give self-serving and self-aggrandizing answers at your expense.

Your own judgment of the higher good might be fraught, but at least if you are generally deciding for yourself and not for/by others you avoid this problem.