- mindless, reasonless, senseless - not marked by the use of reason; "mindless violence"; "reasonless hostility"; "a senseless act"
Antonyms: reasonable, sensible (indirect, via unreasonable)
- reasonless - not endowed with the capacity to reason; "a reasonless brute"
Antonym: rational (indirect, via irrational)
- causeless, reasonless - having no justifying cause or reason; "a senseless, causeless murder"; "a causeless war that never had an aim"; "an apparently arbitrary and reasonless change"
Antonym: motivated (indirect, via unmotivated)