Yes, DUALISMS is a Scrabble word!

Letter values in Scrabble US: D 2, U 1, A 1, L 1, I 1, S 1, M 3, S 1.

Is it a valid word?

DUALISMS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the doctrine that reality consists of two basic opposing elements, often taken to be mind and matter (or mind and body), or good and evil