 The attitude that individual physicists adopt towards this problem is strongly influenced by their intuitions about which theory, general relativity or quantum theory, will have to be modified to achieve a consistent theory of quantum gravity. Spacetime physicists tend to view non-standard quantum evolution as a fairly natural consequence of singular spacetimes: one would not expect all the details of systems at earlier times to be available at later times if they were lost in a singularity. Hawking (1976), for example, argued that the paradox shows that the full theory of quantum gravity will be a theory that does not obey the standard dynamical principles of quantum theory, and he began working to develop such a theory very soon after first promulgating the paradox. (He has since abandoned this position.) Unruh and Wald (2017) develop an extended review and defense of this position. Particle physicists (such as superstring theorists), however, tend to view black holes as being just another state of a quantum field. If two particles were to collide at extremely high energies, they would form a very small black hole. This tiny black hole would have a very high Hawking temperature, and thus it would very quickly give off many high-energy particles and disappear. (Recall, as discussed in  section 5.2  above, that Hawking temperature is inversely proportional to the mass of black hole.) Such a process would look very much like a standard high-energy scattering experiment: two particles collide and their mass-energy is then converted into showers of outgoing particles. The fact that all known scattering processes obey the standard dynamical principles of quantum theory, and above all unitarity, then, seems to give us some reason to expect that black hole formation and evaporation should also do so. 