The origin of the solar system has been a matter for speculation for many centuries, and since the time of Newton it has been possible to apply scientific principles to the problem. A succession of theories - starting with that of Pierre Laplace in 1796 - have gained general acceptance, only to fall from favour due to their contradiction in some basic scientific principle or new heavenly observation. Modern observations by spacecraft of the solar system, the stars and extra-solar planetary systems continuously provide new information that may be helpful in finding a plausible theory, but importantly also give new constraints for any such theory to satisfy. This work begins by describing historical (pre-1950) theories and illustrating why they became unacceptable. The main part then critically examines five extant theories - including the current paradigm, the Solar Nebula Theory - to determine how well they fit in with accepted, scientfic principles and observations. This analysis shows that the Solar Nebula Theory satisfies such principles and observational constraints no better than its predecessors. The Capture Theory - put forward by the author - fares better and also indicates an initial scenario leading to a causal series of events that explains all the major features of the solar system.