This paper has three parts. First, we establish some of the basic model theoretic facts about M T , the Tsirelson space of Figiel and Johnson [20]. Second, using the results of the first part, we give some facts about general Banach spaces. Third, we study model-theoretic dividing lines in some Banach spaces and their theories. In particular, we show: (1) M T has the non independence property (NIP); (2) every Banach space that is ℵ 0 -categorical up to small perturbations embeds c 0 or p (1 p < ∞) almost isometrically; consequently the (continuous) first-order theory of M T does not characterize M T , up to almost isometric isomorphism.