 There are enough of these to display the space-like aspect.For example, if "X" is the classifying topos "S"["T"] for a geometric theory "T", then the universal property says that its points are the models of "T" (in any stage of definition "Y").A geometric morphism ("u"∗,"u"∗) is "essential" if "u"∗ has a further left adjoint "u"!, or equivalently (by the adjoint functor theorem) if "u"∗ preserves not only finite but all small limits.