Consider: SANITY VS. INSANITY

san·i·ty | ˈsanədē |

noun

the ability to think and behave in a normal and rational manner; sound mental health: I began to doubt my own sanity.

• reasonable and rational behavior: the next few years saw several appeals for sanity from top scientists.

insane

adjective

1 mentally ill, severely mentally disordered, of unsound mind, certifiable, psychotic, schizophrenic; mad, mad as a hatter, mad as a March hare, deranged, demented, out of one’s mind, out of one’s head, not in one’s right mind, sick in the head, unhinged, unbalanced, unstable, disturbed, crazed, crazy, hysterical; Latin non compos mentis; British sectionable; informal raving mad, stark raving mad, not all there, bonkers, cracked, bats, cuckoo, loony, loopy, nuts, nutty, nutty as a fruitcake, screwy, bananas, off one’s rocker, off one’s head, off one’s chump, off one’s nut, off the wall, around the bend; British informal crackers, barmy, batty, barking, barking mad, stark staring mad, off one’s trolley, round the twist, as daft as a brush, not the full shilling, away with the fairies; North American informal buggy, nutsy, nutso, out of one’s tree, wacko, squirrelly; Canadian & Australian New Zealand informal bushed; New Zealand informal porangi. ANTONYMS sane

2 he made an insane suggestion: extremely foolish, idiotic, stupid, silly, senseless, nonsensical, pointless, absurd, ridiculous, ludicrous, farcical, laughable, preposterous, weird, bizarre…