One person's craziness is another person's reality.

What looks like madness from the outside often feels like plain common sense from the inside. Our sense of what is normal is shaped by where we grew up, what we have lived through, and who surrounds us, so when someone behaves in a way we can't follow, we tend to blame their mind rather than our limited view. The line puts reality on a sliding scale: each person lives in a world that makes sense to them, and "crazy" is often just the word we use for a world we haven't visited.

This fits the outlook that runs through Tim Burton's films, which are full of misfits like Edward Scissorhands and Beetlejuice, where the outcast is often more sympathetic than the respectable neighbors. It also echoes the old philosophical idea that perception is always partial and that social norms are agreements, not laws of nature.

In practice, you might use it when a relative or coworker holds a belief or habit that baffles you. Before dismissing them, you could ask what in their life makes it feel obvious, and listen for the answer. You needn't agree, but you'll understand more and judge less.