In a generally sympathetic review of The Dialectical Biologist (Maynard Smith, 1986), and in personal conversations, John Maynard Smith argued that the development of a rigorous, quantitative mathematical systems theory makes dialectics obsolete. Engels' awkward "interchange of cause and effect" can be replaced by "feedback", the mysterious "transformation of quantity into quality" is now the familiar phase transition or threshold effect, while "even in my most convinced Marxist phase, I could never make much sense of the negation of the negation or the interpenetration of opposites". He could have added that hierarchy theory grasps some of the insights of "integrated levels' or "overdetermination".