  The recent BICEP2 measurement of B-modes in the polarization of the cosmic
microwave background suggests that inflation was driven by a field at an energy
scale of $2\times 10^{16}$ GeV. I explore the potential of upcoming CMB
polarization experiments to further constrain the physics underlying inflation.
If the signal is confirmed, then two sets of experiments covering larger area
will shed light on inflation. Low resolution measurements can pin down the
tensor to scalar ratio at the percent level, thereby distinguishing models from
one another. A high angular resolution experiment will be necessary to measure
the tilt of the tensor spectrum, testing the consistency relation that relates
the tilt to the amplitude.
