 The secondary literature on this topic is enormous. The following list is highly selective, and entries are included by meeting at least one of the following criteria: good representative of a standard reading of the argument; influential source, primary or secondary; useful collection of items meeting one or other of the previous two criteria; useful survey; item making recent and significant progress in the understanding and assessment of the argument; source drawn on in the writing of this article; item mentioned in the main text of this article.