Killing the Straw Man: Does BICEP Prove Inflation? James 13. Dent Department of Physics, University of Louisiana at Lafayette, Lafayette, LA 70504, USA, Lawrence M. Krauss Department of Physics and School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA, and Mount Stromlo Observatory, Research School of Astronomy and Astrophysics, Australian National University, Weston, ACT, Australia, 2611 Harsh Mathur Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079 The surprisingly large value of r, the ratio of power in tensor to scalar density perturbations in the CMB reported by the BICEP2 Collaboration provides strong evidence for Inflation at the GUT scale. In order to provide compelling evidence, other possible sources of the signal need to be ruled out. While the Inflationary signal remains the best motivated source, the current measurement unfortunately still allows for the possibility that a comparable gravitational wave background might result from a self ordering scalar field transition that takes place later at somewhat lower energy. However even marginally improved limits on the possible isocurvature contribution to CMB anistropies could rule out this possibility, and essentially all other sources of the observed signal other than Inflation. The recent claimed observation of primordial gravita- tional waves [1] provides a dramatic new empirical win- dow on the early universe. In particular, it provides the opportunity, in principle, to definitively test the inflation- ary paradigm[2, 3], and to explore the specific physics of inflationary models. However, while there is little doubt that inflation at the Grand Unified Scale is the best mo- tivated source of such primordial waves (e.g. [4-7], it is important to demonstrate that other possible sources cannot account for the current BICEP2 data before def- initely claiming Inflation has been proved. A surprisingly large value of r,