 The ‘Historical, Plain Method’ is apparently to give a genetic account of how we come by our ideas. Presumably this will reveal the degree of certainty of the knowledge based on such ideas. Locke’s own active involvement with the scientific movement was largely through his informal studies of medicine. Dr. David Thomas was his friend and collaborator. Locke and Thomas had a laboratory in Oxford which was very likely, in effect, a pharmacy. In 1666 Lord Ashley, one of the richest men in England, came to Oxford in order to drink some medicinal waters there. He had asked Dr. Thomas to provide them. Thomas had to be out of town and asked Locke to see that the water was delivered. As a result of this encounter, Ashley invited Locke to come to London as his personal physician. In 1667 Locke did move to London becoming not only Lord Ashley’s personal physician, but secretary, researcher, political operative and friend. Living with him Locke found himself at the very heart of English politics in the 1670s and 1680s.