  Mode coupling theory (MCT) appears to explain several, though not all,
aspects of the glass transition in colloids (particularly when short-range
attractions are present). Developments of MCT, from rational foundations in
statistical mechanics, account qualitatively for nonlinear flow behaviour such
as the yield stress of a hard-sphere colloidal glass. Such theories so far only
predict shear thinning behaviour, whereas in real colloids both shear thinning
and shear thickening can be found. The latter observation can, however, be
rationalised by postulating an MCT vertex that is not only a decreasing
function of strain rate (as found from first principles) but also an increasing
function of stress. Within a highly simplified, schematic MCT model this can
lead not only to discontinuous shear thickening but also to complete arrest of
a fluid phase under the influence of an external stress (`full jamming').
