The different nature of cosmology

Cosmology has progressed in the past 35 years from a mainly mathematical an d philosophical exercise to an important branch of both astronomy and physi cs, and is now part of mainstream science, with a well-established Standard Model confirmed by various strands of evidence. Nevertheless, because of i ts nature, it is different from any other branch of the natural sciences. T he major issue causing the difference is the uniqueness of the object of st udy - the universe as a whole - together with its role as the background fo r all the rest of physics and science, the resulting problems being accentu ated by its vast scale and the extreme energies occuring in the early unive rse. We are unable to manipulate its originating conditions, and there are limitations on our ability both to observe to very distant regions and very early times and also to test the physics relevant at the earliest times. C onsequently it is inevitable that specific philosiphical choices will to so me degree shape the nature of cosmological theory.