My assignment is to consider the inter? face from the viewpoint of a populational biologist?in so far as an animal behaviorist can represent that position?and I should like to begin by quoting a zoologism from an essay that Isaiah Berlin wrote in 1951 on Tolstoy. He tells us that, There is a line among the fragments of the Greek poet, Archilochus, which says: 'The fox knows many things, but the hedgehog knows one big thing.' Scholars have diifered about the correct interpretation of these dark words, which may mean no more than that the fox, for all his cunning, is defeated by the hedgehog's one defense. But, taken figuratively, the words can be made to yield a sense in which they mark one of the deepest differences which divide writers and thinkers, and, it may be, human beings in general. He goes on to propose that Tolstoy's greatness stems from being a fox by nature yet striving to be a hedgehog. I want to suggest that a similar ideal may be appropriate for scientists as well. I think of the typical organismal biologist as something of a fox, elucidating the structural or physiological basis of some property of the organism, finding his ultimate satisfaction in the completion of that undertaking, and then seeking another knot to unravel. He is inclined to be an empiricist. Ecologists, evolutionary biologists, and some animal behaviorists are more often, I think, hedgehogs, grappling with unknowns which the individual investigator can rarely hope to understand completely even in a lifetime. Here we find more theorizing and?dare I say it?a certain proclivity towards mysticism. Thus, I wish to distinguish organismal and populational biolo? gists on the basis of their predominant methodology rather than on the basis of their subject matter, although it is obvious that the two are interdependent, and that the biases of each are productive and appropriate to the nature of the problems with which they deal. It should be clear that I am not trying to make a distinction between good and bad research. I take it for granted that all good research has relevance beyond its immediate context, whatever the level of analysis. I am thinking, rather, of the strategy that guides the choice of direction in which to pursue a problem, once initiated. The inclination to pursue a reductionist ap? proach is characteristically that of a fox. A hedgehog will more readily look in the other direction, to the more emergent properties of the phenomenon under study. Whether a biologist is working with populations, or at the organizational or molecular level, he can work creatively with either approach, but populational biology seems to be a special haven for hedgehogs, presumably because of the nature of the problems in the area. I want to press the case for breeding more hybrids, or should I say for training fedgehoxes, who will be organismal biol? ogists with an evolutionary approach to their subject, and populational biologists, bringing all of the special methods and insights of organismal biologists to the problems they study. I feel some urgency about this need. All over the country, and I suppose all over the world, the curricula in introductory biology are being revised to incorporate the fruits of the revolution in molecular