The tax reform that will pass Congress Wednesday fulfills a major Republican campaign promise, but more important is that it marks a return to the politics of growth after many lean years of envy and income redistribution. It offers hope of broader prosperity after a decade of slow growth and rising inequality.

On the merits, the bill is the most pro-growth tax policy since the Reagan reforms of 1981 and 1986. We should add that it is not as good for individual taxpayers as those two acts. The bill cuts marginal tax rates...