her own work. We were most fortunate that Marjorie Grene was willing to spend a full semester of a recent leave here in Boston, and we have on other occasions sought her participation in our colloquia and elsewhere. Now we have the pleasure of including among the Boston Studies in the Philosophy of Science this generous selection from Grene's philosophical inquiries into the understanding of the natural world, and of the men and women in it. Boston University Center for the R. S. COHEN Philosophy and History of Science M. W. W ARTOFSKY April 1974 PREFACE This collection spans - spottily - years from 1946 ('On Some Distinctions between Men and Brutes') to 1974 ('On the Nature of Natural Necessity').