  By developing a theory of deformations over nilpotent Lie algebras, based on
Schlessinger's deformation theory over Artinian rings, this paper investigates
the pro-l-unipotent fundamental group of a variety X. If X is smooth and
proper, defined over a finite field, then the Weil conjectures imply that this
group is quadratically presented. If X is smooth and non-proper, then the group
is defined by equations of bracket length at most four.
