In this line of thinking, Ellacuría said human reality is unavoidably personal, social and historical. Biology and society are elements of history, which means that they are always in movement. But this should not be confused with historical materialism that says human beings are passive instruments of the forces of history. Human beings certainly inherit constraints constructed in the past but they always have the possibility to transcend them because of their sentient intelligence. Praxis is the name Ellacuría gives to reflected human action aimed at changing reality. Unlike other animals that can only respond mechanically to stimuli from outside, through sentient intelligence and praxis, human beings have to "realise" their existence. Individuals in dialectic interaction with society, have to make out what sort of Ego to have, by using their sentient intelligence, and this implies transcending inherited constraints.