The opposite could be wise, smart, wise, sagacious, or circumspect.
wise
Foolish begins with F and it is the opposite of wise.
Wise
foolish
Careless, foolish, idiotic, stupid, ignorant, senseless, irrational, thoughtless, uneducated, or reckless. Those words are the opposite of wise.
foolish
unwise foolish.
Competent serious.,
The opposite of the word intelligent is unintelligent or stupid.
ANSWER: stupid ,foolish, dum, naive, not smart
The opposite of sagacious is ignorant, careless, foolish or stupid.
Wise. -Dr.RSJameson 01March'08