Popper suffered throughout his life from bouts of depression and hypochondriasis, although he lived to an advanced age. He was a disturbed, difficult youth and began a number of projects that he never finished; this continued even in the first years after World War I, "for Popper a period of loss of direction and constant experimentation" (p. 107). One of his projects was teaching; apparently a student under his care had a fatal accident that seemed to affect Popper in an existential way. After that occurrence, which Hacohen calls the "1925 tragedy" (p. 131), Popper avoided political engagement and focused on his intellectual interests and his professional career, ending his years of rebellion, antibourgeois life style, and unconventional life pattern. Mercifully, Hacohen, a professional historian, spares us from speculative psychoanalytic interpretations of these events. He simply tells us that Popper’s life "represented a singular fusion of hope and anxiety, openness to change and attachment to habit, critical awareness of one’s self and mistrust of friends who refused him blind protection" (p. 148). In The Logic of Scientific Discovery(7), Popper created a model of natural science; he extended this model to social sciences in both The Open Society and Its Enemies(6) and his methodological treatise, The Poverty of Historicism(8).