  We study the parameter space of D-dimensional cosmological Einstein gravity
together with quadratic curvature terms. In D>4 there are in general two
distinct (anti)-de Sitter vacua. We show that for appropriate choice of the
parameters there exists a critical point for one of the vacua, for which there
are only massless tensor, but neither massive tensor nor scalar, gravitons. At
criticality, the linearized excitations have vanishing energy (as do black hole
solutions). A further restriction of the parameters gives a one-parameter
cosmological Einstein plus Weyl^2 model with a unique vacuum, whose \Lambda is
determined.
