Though most well-known as a hymn-writer, the dissenting minister Isaac Watts (1674–1748) was a versatile intellectual, writing on theology and philosophy and wielding an important influence among his contemporaries and later. Beynon's thorough study of Watts's thought helps to redress Alan Sell's comment that Watts ‘deserves more attention than he ordinarily receives’ (p. 1).

Beynon provides a detailed discussion of Watts's work in two parts: ‘Reason and Passion’ and ‘The Revival of Religion’. In the first he considers ‘The role of reason’ and ‘The place of passion’. The four chapters in the second part are ‘The art of preaching’; ‘The need for praise’; ‘The method of prayer’; and a conclusion. These chapters fully explore the complexities of Watts's thought and link his key themes with his practical works. This provides an overall picture of the coherence of Watts's work in its various expressions.

Watts stood in the Puritan tradition, espousing a modified Calvinism, and often quoting important Puritan writers. Overall, his work represents continuity with this stream of English religion. But Watts was also keenly aware of changing intellectual currents, coming especially through the work of John Locke. Watts took on important dimensions of Enlightenment thought, especially in regard to the role of reason.

For Watts, the right reason with which humans were endowed by their Creator was overthrown and made captive to sinful passions. Thus the will has a major effect on the decisions of the mind. Watts wrote that

Original sin affects all. Only a dramatic change can reverse this situation. Beynon writes that for Watts ‘logic or right reasoning is seen as part of our recovery from the fall and hence part of God's redemptive purposes’ (p. 31). A tension for Watts is that reason and human rationality must be used to defend Christian orthodox theology, but Christian doctrine itself must be recognised as originating from ‘above reason’ – in divine, supernatural revelation.

Human passions are, for Watts, at the centre of the human condition of sin, bringing disorder and difficulties – what he says are ‘our snares and torments’ (p. 85). Passions are a ‘most powerful engine of mischief’ and lead to all manner of sinful behaviour. Conversion – which entails faith in Jesus Christ – is the only remedy for disordered passions. Regeneration, Watts says, means ‘a great and holy change, wrought in the powers of your soul, your understanding, will and affections, by the Spirit of God’ (p. 90). In a sermon on God's healing of a lost sinner, Watts speaks on behalf of God who says: ‘“I will heal him; that is, I will renew all his inwards passions, I will renew all his affections”’ (p. 91). God's Spirit reestablishes the harmony of the human faculties. God's divinely created order is reestablished – reason is now the ruler of the faculties. In a hymn on regeneration, Watts wrote that ‘The Spirit, like some heav'nly wind,/Blows on the sons of flesh,/New-models all the carnal mind,/And forms the man afresh’ (p. 91). Beynon indicates that Watts is ‘an early example of what will become common in evangelical theology in the mid-century revivals: an affective element in conversion, rather than a mere acknowledgement of propositional truth’ (p. 91). Here there are affinities with Jonathan Edwards.

Equipped with these convictions, Watts attempted to revive contemporary religion. Beynon focuses on how Watts proceeded through preaching, praise and prayer.

While Watts recognised that Puritan preaching contained much knowledge to inform people – a trait not shared by much preaching of his own day – he also critiqued Puritan sermons for their complexities. He compared them to Ezekiel's vision of the dry bones by saying, ‘There were very many in the valley, and lo, they were very dry’ (p. 127). Instead, Watts sought an ‘art of persuasion’, using clear and plain language. He wanted to affect the mind, will and passions of sermon-hearers. The preacher strives to excite a love for God in the whole person. Says Beynon, ‘Watts’ ideal preaching combines the “clear and distinct ideas” of Locke with the excited heart of the enthusiast’ (p.139).

While Watts encouraged the praise of God through the singing of Psalms, his paraphrases of them (for which he received criticism), and hymn texts moved Christian praise in worship to wider ways. His books in short ‘revolutionized the praise of the church’ (p. 147). Watts's impelling passion here was his conviction that the praise of God is the purpose of human existence and a primary way of praising God and acknowledging who God is comes from using the human voice in song. Watts's renovation of the praise of the Church was ‘the area he succeeded in above all others’ (p. 168).

Watts also wrote to reform the practice of prayer, which is part of Christian worship and duty. He advocated free prayer, praying with understanding and affection (p. 177). This combines his emphases on the right use of reason with support of Christian passions, rightly directed to God. Passionate prayer can be reasonable; and prayer should be a continuing spiritual practice, led by the Holy Spirit (p. 186). This will help in ‘returning glory’ to the Churches (p. 191).

Beynon's strong study explains the strands of Watts's thought, shows their interconnections, and also locates Watts more clearly than before in his historical contexts and in relation to other theologians and philosophers. This is an important contribution. The book's extensive bibliography is also a valuable resource. Beynon's work opens directions for further research. It provides a solid foundation in establishing how remarkable Watts's views were as they developed and as they stood in relation to the views of others.