Key points are not available for this paper at this time.
Dirac showed that the existence of magnetic monopoles would imply quantization of electric charge. I discuss the converse, and propose two 'principles of completeness' which I illustrate with various examples. Presented at the Dirac Centennial Symposium, Tallahassee, Dec. 6-7, 2002.
J. Polchinski (2004) studied this question.