Debru, Claude

Claude Debru My point is not a comment on reductionism, but a comment on the movement of the planets. We know since Poincare that the movement of the planets is chaotic, which means that it would be predictable if we would have the knowledge of the initial conditions of the system. But in the ignorance of this data of the initial conditions, it remains unpredictable. So I think this qualifies some ideas, perhaps. I don t know how it fits into the framework about reductionism - because you mentioned the movement of the planets. 

Claude Debru I m very much interested in the distinction you introduced in this discussion between how possible and necessarily. These ideas of possibility and necessity have obviously deep philosophical roots and the idea of possibility is extremely difficult anyway. My question would be the following one - Would you agree that when you ask the question of how possible, how possibly, you have to get an idea of all the possibilities which are involved before giving the answer Then, do you think biologists have really the idea of all possibilities which are run at a certain level of biological evolution ... 

Claude Debru. Yes, a very small remark, which has been already done in a way. I didn t understand from Michel Morange s argument on this gene that this particular gene controls maternal behaviour. I understood only that it controls hypothalamus development, which is something perhaps different. What about this gene in males Has it been made knocked-out in males ... 

Another example, and here Claude Debru will probably disagree with me, where co-operative phenomena have been given reductionistic explanation very, very successfully is the allosteric model, where, even though the model is complicated, which is a separate issue, it s purely mechanistic interactions that ultimately do give explanation. 

Claude Debru Not quantitative a statistical model based on correlations, not causation, I would say. 

Claude Debru Universite Paris 7, 2 Place Jussieu, 75251 Paris Cedex 05, France... 

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