Force is a stat found only in EarthBound Beginnings that decreases the chance of the character being affected by Puzzled, Confused, or Hypnosis (however, Stone will always hit). This stat resembles the IQ stat in the other games of the Mother series.
Force can be used to calculate how much PP your character will have (with the exception on non-PSI characters) at the next level up. The formula is: 1.5 * Force = max. PP at next level up.