  We show that the strong coupling physics inherent to the insulating Mott
state in 2D leads to a jump in the chemical potential upon doping and the
emergence of a pseudogap in the single particle spectrum below a characteristic
temperature. The pseudogap arises because any singly-occupied site not
immediately neighbouring a hole experiences a maximum energy barrier for
transport equal to $t^2/U$, where $t$ is the nearest-neighbour hopping integral
and $U$ the on-site repulsion. The resultant pseudogap cannot vanish before
each lattice site, on average, has at least one hole as a near neighbour. The
ubiquituity of this effect in all doped Mott insulators suggests that the
pseudogap in the cuprates has a simple origin.
