  For a quasi-compact quasi-separated scheme X and an arbitrary scheme Y we
show that the pullback construction implements an equivalence between the
discrete category of morphisms Y --> X and the category of cocontinuous tensor
functors Qcoh(X) --> Qcoh(Y). This is an improvement of a result by Lurie and
may be interpreted as the statement that algebraic geometry is 2-affine.
Moreover, we prove the analogous version of this result for Durov's notion of
generalized schemes over F_1.
