a] The first is that, given the common origin of logical-arithmetical and geometric structures from sensorimotor actions, space remains at all levels a necessary (though not sufficient) mediator between the subject and objects. This is the reason why, even in theoretical physics, group structures, for example, serve to explain phenomena that retain a spatial dimension, since wherever there is movement—real or virtual—some "field" intervenes with its domain of action. b] The second, which similarly derives from this common origin, is the isomorphism of the geometry of the space of objects, in its diverse varieties, and of certain aspects of the geometry of the subject (initially subordinated to the former, but becoming increasingly rich). Indeed, while the subject only proceeds by successive approximations in its deductive reconstructions of the dynamics of objects—without ever being certain of having reached the limit—the spatial characteristics of experience are transparent to reason to the extent that they remain geometric.