Isaac Watts belonged to the Independents, a sect which in the first half of the eighteenth century was less tainted with Socinianism than any of 'the three denominations.' His 'Treatise on the Christian Doctrine of the Trinity,' and that entitled 'The Arian invited to the Orthodox Faith,' were professedly written in defence of the Catholic doctrine. The former, like most of Dr. Watts's compositions, was essentially a popular work. 'I do not,' he writes, 'pretend to instruct the learned world. My design here was to write for private and unlearned Christians, and to lead them by the fairest and most obvious sense of Scripture into some acquaintance with the great doctrine of the Trinity.'[447] In some respects his work is very effective. One point especially he brings out more forcibly than almost any other writer of his day. It is what he calls 'the moral argument' for the Trinity. There is real eloquence in his appeal to the 'great number of Christians who, since the Apostles, under the influence of a belief in the Divinity of the Son and the Spirit, have paid divine honours to both, after they have sought the knowledge of the truth with the utmost diligence and prayer; when they have been in the holiest and most heavenly frames of spirit, and in their devoutest hours; when they have been under the most sensible impressions of the love of the Father and the Son, and under the most quickening influences of the Blessed Spirit himself; in the devotions of a death-bed, and in the songs and doxologies of martyrdom.' 'Now can we,' he asks, 'suppose that in such devout and glorious seasons as these, God the Father should ever thus manifest His own love to souls that are degrading Him by worshipping another God? That Christ Jesus should reveal Himself in His dying love to souls that are practising idolatry and worshipping Himself instead of the true God?'