  We show that in a locally lambda-presentable category, every
lambda(m)-injectivity class (i.e., the class of all the objects injective with
respect to some class of lambda-presentable morphisms) is a weakly reflective
subcategory determined by a functorial weak factorization system cofibrantly
generated by a class of lambda-presentable morphisms. This was known for
small-injectivity classes, and referred to as the "small object argument". An
analogous result is obtained for orthogonality classes and factorization
systems, where lambda-filtered colimits play the role of the transfinite
compositions in the injectivity case. Lambda-presentable morphisms are also
used to organize and clarify some related results (and their proofs), in
particular on the existence of enough injectives (resp. pure-injectives).
