What good is randomization in Randomized Controlled Trials?

EBM advocates require studies to be properly randomized in order to be judged high quality. But on the face of it, randomization is an odd virtue, since it introduces a chance element and so also an element of avoidable ignorance into the scientific process. Some theorists (e.g.
Bayesians) reject the requirement for randomization, while others accept it—but for different reasons.

We look at the arguments surrounding its justification.
Core reading:
Elwood, M. (2007) Critical Appraisal of Epidemiological Studies and Clinical Trials OUP. Chapter 6, parts 1-2,
Papineau, D. (1994) The virtues of randomization. British Journal for the Philosophy of Science, 45:437–50.
Worrall, J. (2007) Why there’s no cause to randomize. British Journal for the Philosophy of Science, 58:451–88.