Reason, rationality have appeared always to be essential prerogatives of the human being—"the rational animal." Seen as streaming and centralizing human functioning from and through the faculties of the human mind as it throws out its innumerable rays of attention and builds networks of sense, reason seems to promote understanding throughout the horizon of human reality. The human faculties of reason indeed distinguish man from other living beings—given our striking capacities for differentiating, measuring, evaluating, and selecting in matters of fact and the affairs of life as well as for passing judgments and directing our ways of conduct. But it is doubtful that the reach of the faculties exhibited by these powers alone accounts for the indispensable continuity of "rational" functioning. This is the question that lies at the heart of rationality as such and which prompts reinterpretation in dialogue between Islamic metaphysics and phenomenology/ontopoiesis of life.