Letters to a Philosophical Unbeliever

Letters to a Philosophical Unbeliever (1780) is a multi-volume series of books on metaphysics by eighteenth-century British polymath Joseph Priestley.

Priestley wrote a series of important metaphysics works during the years he spent serving as Lord Shelburne's assistant and companion.

But on interrogating them on the subject, I soon found that they had given no proper attention to it, and did not really know what Christianity was ... Having conversed so much with unbelievers at home and abroad, I thought I should be able to combat their prejudices with some advantage, and with this view I wrote ... the first part of my ‘Letters to a Philosophical Unbeliever’, in proof of the doctrines of a God and a providence, and ... a second part, in defence of the evidences [sic] of Christianity.

[3] In Letters, he continued to defend his thesis, begun in Disquisitions relating to Matter and Spirit and The Doctrine of Philosophical Necessity Illustrated, that materialism and determinism can be reconciled with a belief in God.

The text addresses those whose faith is shaped by books and fashion; Priestley draws an analogy between the skepticism of educated men and the credulity of the masses.