  We prove the (2,1)-categorical analogue of the small object argument and give
a (2,1)-model structure on the category of small coherent categories, coherent
functors and natural isomorphisms. It is induced by a higher dimensional
example of a reflective factorisation system, determined by the full
subcategory of pretoposes. We prove it to be right proper and the generating
trivial cofibrations are described. Whitehead's theorem gives conceptual
completeness.
