  One of the most intriguing aspects of cuprates is a large pseudogap
coexisting with a high superconducting transition temperature. Here, we study
pairing in the cuprates from electron-electron interactions by constructing the
pair vertex using spectral functions derived from angle resolved photoemission
data for a near optimal doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ sample that
has a pronounced pseudogap. Assuming that that the pseudogap is {\it not} due
to pairing, we find that the superconducting instability is strongly
suppressed, in stark contrast to what is actually observed. Using an analytic
approximation for the spectral functions, we can trace this suppression to the
destruction of the BCS logarithmic singularity from a combination of the
pseudogap and lifetime broadening. Our findings strongly support those theories
of the cuprates where the pseudogap is instead due to pairing.
