Answer:

sanity

Answer	Crossword Clue
SANITY	Level-headedness
SANITY	Marbles
SANITY	Soundness of mind

SANITY	Sound quality?
SANITY	Marbles, so to speak
SANITY	Reason
SANITY	"Madness put to good use": Santayana
SANITY	Loss of the certifiable
SANITY	Lunatic's lack
SANITY	"Marbles," colloquially
SANITY	Rational state

SANITY	Reasonableness
SANITY	Wholesomeness.
SANITY	Soundness of mind.
SANITY	Lucidity.
SANITY	Reason.
SANITY	Reasonableness.
SANITY	Sweet reasonableness.
SANITY	Beautiful reason.

SANITY	Mental health
SANITY	Soundness
SANITY	Soundness of judgment
SANITY	" . . . there ain't no ... Clause": Chico Marx
SANITY	Mental equilibrium
SANITY	Soundness of reason
SANITY	Soundness, to Skinner
SANITY	Balance

SANITY	Sensibleness
SANITY	Levelheadedness
SANITY	"Madness put to good uses," per George Santayana
SANITY	"A cozy lie," per Susan Sontag
SANITY	Marbles you don't play with
SANITY	Mental soundness
SANITY	Sound powers of mind
SANITY	Wits

SANITY	Clearmindedness