I said of laughter, It is mad: and of mirth, What doeth it?
Laughter - flowing from sensual gratifications.
(It is) (rather, Thou art). Hengstenberg translates (limshok besari), 'to cherish.'
Mad - i:e., when made the chief good. It is harmless in its proper place; yea, the Preacher urges us to enjoy thankfully present goods (Ecclesiastes 2:24).
What doeth it? - of what avail is it in giving solid good? (Ecclesiastes 2:11.)