The transitional situation we are experiencing, in which a book culture coexists with a screen culture, is gradually moving us from a graphic reason to a computational reason. Just as writing gave rise to a way of thinking in which lists, tables and formulae played a key role in modelling knowledge, digital technology is inventing other systems for formatting and transmitting information. Indeed, the development of the network, of a vast cyberspace, induces a particular rationality based on calculation rather than writing, which is the only way to make it intelligible. We can therefore understand that memory architectures, in their contemporary, essentially digital form, are at the heart of a transformation of the human mind. It is still too early to determine exactly what this transformation will entail, but it is important now to sketch the contours of this situation and to explore the avenues that might mark some of its most salient aspects.