All x Everything

Am I more likely to get pregnant if my husband wears boxers rather than briefs?

You'll have an even better chance if he doesn't wear anything at all

Everything é um pronome.

Everything is illuminated.

All é um adjetivo.

All exits were shut down.

Porém, all também pode exercer a mesma função de everything, desde que seguido de complemento.

Thanks for everything.

Thanks for all your help.

Exemplos extras (dicionário Oxford escolar, nona impressão, 2003)

He denied all knowledge of the crime. (all = adjetivo)

I ate all of it. = I ate everything. (all = pronome)

Não esquecer as locuções com all, entre outras:

all in all

not at all