Prima Facie Questions in Quantum Gravity

摘要

The long history of the study of quantum gravity has thrown up a complex webof ideas and approaches. The aim of this article is to unravel this web alittle by analysing some of the {\em prima facie\/} questions that can be askedof almost any approach to quantum gravity and whose answers assist inclassifying the different schemes. Particular emphasis is placed on (i) therole of background conceptual and technical structure; (ii) the role ofspacetime diffeomorphisms; and (iii) the problem of time.