Elsw
Take a jug of milk. Pour some in several glasses. Check contents of each glass. Is it really milk, identical to that in the jug? If yes, hypothesis is supported. If no, then hypothesis fails
Extrapolating in reverse, a person could use various methods to find out their true nature. Once your true nature is established, then we can go from there. Until your true is ascertained, there are limitations for everything else.
S