Peter Anstey writes…
Until now the earliest evidence for Locke making Boyle’s acquaintance is a letter from Dr Ayliffe Ivye to Locke of 20 May 1660. This letter implies that Locke knew Boyle by this time and Ivye recommends to Locke that he ‘lett slippe no occasion’ to develop his acquaintance with Boyle (Locke Correspondence, ed. E. S. de Beer, vol. 1, p. 146). New evidence has now emerged that strongly suggests that Locke knew Boyle at least two years earlier, in 1658.
Locke’s earliest surviving medical notebook, Bodleian Library MS Locke e. 4, was in use in the 1650s. There appears to be no indication from its contents that Locke used it after 1658. In this notebook there are a number of entries deriving from a person called M. B. Could this refer to M[r] B[oyle]? The content of one of these entries confirms that it does.
On page 59 Locke made the following entry under the marginal title ‘Obstructio’:
A lady that had been sick a great while of the * & used very much physic to noe purpose was curd presently by useing her owne water M. B.
Locke almost certainly heard this from Boyle, because in Usefulness of Experimental Natural Philosophy (1663), which he was composing in the late 1650s, Boyle relates:
I knew an ancient Gentlewoman, who being almost hopeless to recover of divers Chronical Distempers (and some too of these abstruse enough) was at length advised, instead of more costly Physick, to make her Morning-draughts of her own Water; by the use of which she strangely recovered, and is, for ought I know, still well. (Boyle Works, eds Hunter & Davis, vol. 3, p. 385)
It is unlikely that this entry was made before 1658 because in this notebook, apart from some very early entries at the end, Locke seems to have made entries in chronological order and ‘Obstructio’ is preceded by references to Marin Cureau de la Chambre’s A Discourse on the Principles of Chiromancy (London, 1658) on pages 25–6.
There is an entry derived from M. B. that precedes the one quoted above (MS Locke e. 4, p. 43), it occurs after the entry from de la Chambre. So, there are no grounds on the basis of this notebook for claiming that Locke had met Boyle before 1658.
What all of this shows is that Locke met Boyle at the very time when the latter was formulating his new approach to natural philosophy that he came to call experimental philosophy.