  A non-band theory is developed to describe the superconductor-insulator (SI)
transtition in resistively shunted, single Josephson junctions. The $I-V$
characteristic is formulated by a Landauer-like formula and evaluated by the
path-integral transfer-matrix method. The result is consistent with the recent
experiments at around 80 $mK$. However, the insulator phase shrinks with
decreasing temperature indicating that the single Josephson junction becomes
all superconducting at absolute zero temperature, as long as dissipation is
present.
