The aim of the presentation will be to try to establish a plausible bridge between humanities and the neuroscience on the basis of Paul Ricoeur's concept (1) of the capable person that he defines as a rational and conscious individual engaged in social relationships and with personal identity, in other words taking "oneself as another". Will the neuroscience, in particular cognitive neuroscience, bring any help in our understanding of the capable person and conversely can one anticipate an impact of such debate on the evolution of the neuroscience ?

A first paradox is raised with the universal species-specific traits of the brain of Homo sapiens qualified by Aristoteles as a "rational and social animal". The progress of genomics reveals a remarkable non linear relationship between the fast increase of anatomical complexity of the brain (from primitive mammals up to humans) compared to the modest changes in genome organisation which account for it. From mice to men the number of genes remains nearly the same, with very modest sequence differences between chimpanzee and humans (only about 1.2 %). What happened to the relationship between genome and brain phenotype in the course of evolution which made the brain human (2) ? The answer suggested is based upon the spatio-temporal pattern of developmental gene expression.

A second paradox concerns the apparent contradiction between the concept of a species-specific genetic envelope of human brain organisation and the genesis of a rich cultural diversity. The answer proposed relies on the mode of development of brain connections. Instead of a rigid errorless wiring process, brain networks are assumed to develop through multiple phases of exhuberance followed by steps of selective stabilisation/elimination by evoked/spontaneous activity (2,3) and evaluation/reward systems are assumed to play critical roles in these selection processes. In the course of mammalian evolution, the duration of the period of synaptogenesis increases from a few weeks in the rat to almost 15 years in humans. As a consequence, an epigenetic appropriation of developing circuits by cultural processes, such as spoken/written language, symbolic systems, moral rules... takes place. As a consequence an important epigenetic variability develops between individual brains (even from genetically identical individuals). Yet, the mathematical formulation of the selective stabilisation theory states (3) that "different learning inputs may produce different connective organisations and neuronal functional abilities but the same behavioral abilities". Communication between individual brains at the social level then becomes possible. The human individual becomes a social person.

A third paradox concerns the neural bases of consciousness. We are at the highest and most enigmatic level of brain functions and the first question is whether or not a science of consciousness is plausible ? The answer is yes : on both experimental and theoretical grounds. It is indeed possible to collect objective recordings of conscious versus non conscious information processing in the brain. and to account for them by neurocomputational models (4,5) for access to consciousness. The neuronal workspace hypothesis (4) proposed assumes that conscious processes mobilize cortical pyramidal neurons with long range horizontal connections (mostly from cortical layers II and III) which are specially abundant in the prefrontal cortex and create a global interconnectivity at the brain scale level. The model includes the reference to the self, personal memories, internalized rules and social conventions together with the representation of "states of mind" of others as well as a "violence inhibition" mechanism. A neuroscience of the capable conscious person then becomes a realistic, but still in progress, project (5) .

The last issue to be discussed will be the plausibility of Ricoeur's ethical project of a "good life with and for others in just institutions...» in a present world of dramatic conflicts (1) . The reference to objective knowledge and scientific enquiry as a force of reconciliation at the world scale level will be suggested as a step toward a modern secular humanism (5) .

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(1) Changeux, J.P.,& Ricoeur, P., 1998, La Nature et la Règle, Odile Jacob, Paris ; english translation DeBevoise What Makes Us Think? 2000 Princeton.

(2) Changeux, J.P., 1983, l'Homme neuronal ; english translation Garey Neuronal Man : The Biology of Mind, 1985 Princeton University Press.

(3) Changeux, J.P., Courrège, P. & Danchin, A., 1973, Proc. Natl. Acad. Sci. ( USA) 70 :2974-2978 ; Changeux JP, Danchin A. Selective stabilisation of developing synapses as a mechanism for the specification of neuronal networks, Nature. 1976 264:705-12.

(4) Dehaene, S., Kerszberg, M. & Changeux, J.P., 1998, Proc. Natl. Acad. Sci. (USA) 95 :14529-14534 ; Dehaene, S. & Changeux, J.P. 2004. In : "The cognitive neurosciences III", X Consciousness, M.S. Gazzaniga ed. MIT Press, pp. 1145-1158 ; Dehaene, S., Changeux, J.P., Naccache, L., Sackur, J. & Sergent, C. 2006. TRENDS in Cogn. Sci. n°5, 10 :193-238.

(5) Changeux, J.P. 2002, L'Homme de Vérité Odile Jacob ; english translation DeBevoise The Physiology of Truth : Neuroscience and Human Knowledge, 2004 Harvard University Press.