  We prove, without set theoretic assumptions, that every locally presentable
category C endowed with a tractable cofibrantly generated class of cofibrations
has a unique minimal (or left induced) Quillen model structure. More generally,
for any set S of arrows in C we construct the minimal model structure on C with
the prescribed cofibrations and making all the arrows of S weak equivalences.
We describe its class of equivalences as the "smallest Cisinski localizer
containing S". Our proof rely on a careful use of the fat small object argument
and J.~Lurie's "good colimits" technology and on the author previous work on
combinatorial weak model categories and semi-model categories. We also obtain
similar results for left semi-model categories.
