 The prediction of singularities is usually taken to be a deep flaw of  GR.[32]  One potential problem with singularities is that they may lead to failures of determinism, because the laws “break down” in some sense. This concern only applies to some kinds of singularities, however. Relativistic spacetimes that are globally hyperbolic have Cauchy surfaces, and appropriate initial data posed on such surfaces fix a unique solution throughout the spacetime. Global hyperbolicity does not rule out the existence of singularities, and in particular the FLRW models are globally hyperbolic in spite of the existence of an initial singularity. The threat to determinism is thus more qualified: the laws do not apply “at the singularity itself” even though the subsequent evolution is fully deterministic, and there are some types of singularities that pose more serious threats to determinism.