I first met David Hull in the fall of 1968, at the first meeting of the Philosophy of Science Association, being held in Pittsburgh. He was one of a very few people, including Ken Schaffner, Marjorie Green, and (although still a graduate student) Bill Wimsatt, who were breaking away from the hegemony (I've always wanted to use that word!) of the physical sciences and turning to the biological sciences as sources of great philosophical interest. I was five years younger than he, far behind him in accomplishments (he had already published several major papers), and very nervously about to give my first presentation at a professional meeting. No one could have been kinder or more supportive than he, and we started a friendship that was never marred by an unkind word, a friendship that ended yesterday with David's death at the age of 75 from pancreatic cancer.

David Hull was a graduate of the program in History and Philosophy of Science at Indiana University, and when I first met him was a junior member of the Philosophy Department at the University of Wisconsin at Milwaukee. He stayed there for twenty years, moving then to Northwestern University, from which he retired ten years ago. David was deeply influenced by two of his teachers at IU, Norwood Russell Hanson and Michael Scriven. Not only did they instill in him a lifelong belief that philosophy of science must be complemented by the history of science -- his first book-length publication, Darwin and His Critics (1973), was an edited volume of scientific responses to Darwin's Origin of Species -- but also they made him somewhat wary of the then- dominant, logical empiricist philosophy (as exemplified by the writings of Ernest Nagel and Carl Hempel).

It would perhaps be too strong to say that David was an anti-reductionist and a holist -- he always had too much down-to-earth common sense to embrace a philosophy that at times veers towards the neo-vitalistic -- but would not be entirely inaccurate to say that there was a flavor of these positions about his work. With respect to reduction, his second book, the very influential The Philosophy of Biology (1974), took a strong stand against the belief that Mendelian genetics is simply something that pops out deductively from molecular genetics. David saw the relationship as far more complex and messy than this, and thought that this was but the tip of an iceberg on which the whole logical empiricist Titanic was doomed to crash. He never had much sympathy for those of us who, like Procrustes cutting off his victim's feet to fit the bed, would push and mold and lop and trim our science to fit our preconceived philosophical notions.

(If you hear echoes of a junior Michael Ruse being suitably chastised by an older friend, you hear correctly. We never ever quarreled but rarely if ever agreed philosophically. I am reminded of Charles Darwin's comment about his close friendship with his fellow magistrate and constant dining companion, Brodie Innes, the vicar of Downe. Darwin said that on one memorable occasion they found themselves in agreement and spent the rest of the meal in astonished silence, convinced that the other was very ill!)

With respect to holism, David's inclination this way came through most strongly with his strong support for zoologist Michael Ghiselin's thesis that species are not classes but biological individuals in their own right. David defended this position with much vigor, bringing both historical and philosophical arguments to bear on the topic. But this was more than something of technical interest to him. David was gay, and proudly so. For him, the species-as-individuals thesis was intensely personal. If you categorize species in terms of groups of reproductively connected organisms (the so-called "biological species" definition), then you are not only turning your back on their past (which as a Darwinian David thought inappropriate) but you are making the condition or criterion of species membership something to do with interbreeding. As a gay man, David was not interesting in interbreeding actually or potentially -- and said so, strongly, many times. (It was a theme behind his presidential address to the Philosophy of Science Association.) Species as individuals pays attention both to history and to the inherent worth of every part of the group, whatever their breeding habits or inclinations may be.

David Hull was a fully paid up member of what one might call the "Chicago School" of evolutionary epistemologists -- other members being historian Robert J. Richards, philosophers Bill Wimsatt and Stephen Toulmin, and social psychologist Donald Campbell. This is the position that sees scientific-theory change as being analogous (perhaps even at one with) biological change -- you have new ideas (mutations), competition between them (struggle), and then one being chosen (selection), and so change occurs (evolution). David used this philosophy as the ground for his major work on the debates about systematics. Science as a Process (1988) was based not only on a deep understanding of the relevant science but also on detailed interviews that he had had with leading controversialists. What was particularly interesting was the way in which David introduced sociological ideas about the influence of older scientists on younger scientists and about how this was a reciprocal relationship, with the younger scientists needing support and the older scientists needing people to carry on their thinking. In a cultural sense we are all selfish genes, doing what we do in order to maximize our representation in the next generations.

David may or may not have been right about all of this. What I can say is that absolutely none of it applied to him. He worked non-stop for the good of the profession, sitting on one boring committee after another. He read one piece of work after another, always sending back detailed comments no matter how awful the piece may have been. He ran a series on the conceptual foundations of science for Chicago University Press, a series that produced a dazzling number of really important books. He encouraged and criticized and promoted the work of others without cease. Entirely typically, for example, when he and I edited the Cambridge Companion to the Philosophy of Biology, he insisted that we not be contributors but that we make the space for a couple of younger philosophers. And he did it all entirely out of Humean sentiment, because he loved other people.

With the coming of HIV, the 1980s was a very stressful time for the gay community. Many of David's friends fell sick and died. These included his lover Dick Wellman. David cared for many of the sufferers and then, as the epidemic died down somewhat, rebuilt his life and carried on, still helping and sponsoring younger people both in the profession and in the gay world of Chicago. There was no reason to feel sorry for him but I sensed that old age started to come rather more quickly than he or his friends had anticipated. He was happy to retire at 65 (in 2000) and although he kept up some writing, it was never again done with the intensity of youth. One happy consequence was that now he was more willing to take vacations for their own sake and he and I enjoyed several together, to France, to Mexico, to Britain. On some of the trips, I took along my then-teenage daughter Emily and they were firm friends.

David Hull was short. I doubt he stood five foot three in his stocking feet. He was the biggest man I ever knew.

Shortly after the Beagle voyage, Charles Darwin dashed up to Scotland to look at the celebrated "roads" of Glen Roy, a valley just off the Great Glen on the west of Scotland. Everyone knew that these roads were the remains of beaches formed by a large body of water. The question was whether this was a lake or the sea, and in either case where is it now? Darwin was convinced that it was the sea and that it is gone because the land has risen. This would support Charles Lyell's "grand theory of climate," which saw the surface of the globe rather like a giant waterbed, with one area sinking and another area rising in unison. Darwin wrote a paper to this effect with all sorts of ad hoc hypotheses showing why we do not find the expected evidences of marine animals. A year or two later, the then-Swiss (later American) ichthyologist Louis Agassiz came up to Glen Roy and at once showed that there had been a glacier, now melted, that held in a lake. Darwin was absolutely and completely wrong (as he later somewhat reluctantly admitted).

This photo is of the two of us, David Hull on the left and Michael Ruse on the right, taken in 2005 at the mouth of Glen Roy in Scotland. We had driven up to look at the Glen, in pouring rain, along a very narrow and winding road. Suddenly it all opened out and we could look down the valley. There indeed were the roads, incredibly impressive even in the bad weather. (You can just see them to the left in the photo.) It was a great thrill but we did not linger!

Michael Ruse