This article examines the Kantian thesis of the a priori nature of our knowledge of space. Because it makes the representation of objects possible as external to us and all others, and consequently, as distinct and individualized, space (whatever its structure may be) claims the status as necessary condition and as apriori possibility of all knowledge. However, in the light of various physical, psychological and philosophical considerations, it seems that the particular structure allocated by Kant to space (i.e. uniqueness, infinity, continuity, homogeneity, isotropy, Euclidean character and three-dimensional character) is neither necessary nor a priori but is rather contingent and dependent on experience. For this reason a pragmatist relativization of the transcendental approach appears to be necessary: the structure of space which makes knowledge possible is not apriori in an absolute sense, but rather, it is determined within the context of a certain practice, which is characterized by a certain mode of interaction with the environment and reveals particular empirical constraints to which this spatial structure must fit.