In some inflationary scenarios, one of the key assumptions of the singularity theorems is violated during the inflationary epoch (i.e., the assumption that + 3p/c > 0). Because of this we cannot infer that there must have been an initial singularity; there may have been, but it is also possible that these universes are eternally old. See Edward W. Kolb and Michael S. Turner, The Early Universe (Reading: Addison-Wesley Publishing Company, 1990).