Encyclopaedic philosopher and founder of science of logic and several other branches of science. Marx called him the greatest thinker of antiquity; wavered between materialism and idealism; recognised four "prime causes" - matter (passive possibility of becoming), form (essence, activity), the beginning of motion and aim; regarded nature as successive transitions from "matter" to "form" and back; saw logical forms as forms of Being, a view which is close to consistent materialism; in theory of knowledge distinguished between Established (apodictic) and Probable (opinion) truth, connected by Language.
