  The BRST invariance condition in a highest-weight representation of the
topological ($\equiv$ twisted $N=2$) algebra captures the `invariant' content
of two-dimensional gravity coupled to matter. The standard DDK formulation is
recovered by splitting the topological generators into $c=-26$
reparametrization ghosts+matter +`Liouville', while a similar splitting
involving $c=-2$ ghosts gives rise to the matter dressed in exactly the way
required in order that the theory be equivalent to Virasoro constraints on the
KP hierarchy. The two dressings of matter with the `Liouville' differ also by
their `ghost numbers', which is similar to the existence of representatives of
BRST cohomologies with different ghost numbers. The topological central charge
$\ctop\neq3$ provides a two-fold covering of the allowed region $d\leq1\cup
d\geq25$ of the matter central charge $d$ via $d=(\ctop+1)(\ctop+6)/(\ctop-3)$.
The `Liouville' field is identified as the ghost-free part of the topological
$U(1)$ current. The construction thus allows one to establish a direct relation
(presumably an equivalence) between the Virasoro-constrained KP hierarchies,
minimal models, and the BRST invariance condition for highest-weight states of
the topological algebra.
