Abstract
In one of his earlier essays he offered a sketch of what a philosophy ought to accomplish. It includes elements which have remained constant throughout thirty years of philosophical activity. He wrote then that the task of philosophy remains what it has always been: to "explain, not explain away, the world we all in some sense know." Prodded by the irritant of science and helped with the newly powerful instrument of modern logic, philosophy must build a system of explanation without reduction. His later philosophy vigorously defends non-scientific ways of understanding and resists any capitulation of philosophy to science or logic, but both remain important for an adequate philosophy. The history of philosophy becomes perhaps even more important as time passes. PIP is taken up with long and intricate reflections on philosophers of every time and sort. In his early sketch, nevertheless, the history of philosophy is said to be valuable for avoiding past mistakes. The five errors he singles out have as their counterpart the embryonic concerns of the modal philosophy.