  We classify all non-collapsing Curtis-Tits and Phan amalgams with
$3$-spherical diagram over all fields. In particular, we show that amalgams
with spherical diagram are unique, a result required by the classification of
finite simple groups. We give a simple condition on the amalgam which is
necessary and sufficient for it to arise from a group of Kac-Moody type. This
also yields a definition of a large class of groups of Kac-Moody type in terms
of a finite presentation.
