By analyzing the temperature ($T$) and density ($n$) dependence of the measured conductivity ($sigma$) of 2D electrons in the low density ($sim10^{11}$cm$^{-2}$) and temperature (0.02 - 10 K) regime of high-mobility (1.0 and 1.5 $times 10^4$ cm$^2$/V
s) Si MOSFETs, we establish that the putative 2D metal-insulator transition is a density-inhomogeneity driven percolation transition where the density-dependent conductivity vanishes as $sigma (n) propto (n - n_p)^p$, with the exponent $p sim 1.2$ being consistent with a percolation transition. The `metallic behavior of $sigma (T)$ for $n > n_p$ is shown to be well-described by a semi-classical Boltzmann theory, and we observe the standard weak localization-induced negative magnetoresistance behavior, as expected in a normal Fermi liquid, in the metallic phase.
