The term "reasonablenesses" refers to the quality of being reasonable or having good judgment. The antonyms, or opposite words, for this term could include irrationality, unreasonableness, foolishness, impracticality or illogicality. These terms all imply a lack of sound judgment or the inability to make sensible decisions. While "reasonablenesses" is a positive term indicating good decision-making skills and the ability to think logically, its antonyms suggest a negative connotation of being illogical or making unsound choices. It is important to consider the antonyms of a word in order to gain a fuller understanding of its meaning and implications.