The privacy, real or illusory, afforded by the personal letter allows each participant the philosophical freedom to explore a range of possible opinions, to experiment with different ideas, to hesitate, and to change his or her mind in ways that published articles and books discourage. The private letter also allows the use of language and style of writing to be altered to suit the particular recipient. This is especially evident in Leibniz's correspondence with Des Bosses. Sometimes, however, the intended recipient is not the addressee, as when Leibniz engaged with Locke through Thomas Burnett of Kemney. This situation was not an isolated occurrence in Leibniz's dealings with Locke. In this chapter, we shall see how Leibniz attempted to engage with Locke through a second correspondence and how he adapted the style and presentation of his views, not for the main correspondent, Lady Masham, but for the other intended recipient. We shall also see that the views Leibniz presents confirm his loyalty during this period to an ontology of embodied, perceiving substances.

The correspondence with Damaris Masham began shortly after Lady Masham sent Leibniz a copy of her father's The True Intellectual System of the Universe (TIS) at the end of 1703. Learning that the book was on its way, Leibniz's first letter was intended to thank her in advance.