presbytery. He mentions (Case, 1715, p. 286) that he had received instruction and personal kindness from John Marck, professor of divinity at Leyden from 1689 to 1731. His brother Matthew (1673–1756), minister at Pencaitland, Haddingtonshire, was entered at Leyden as a divinity student on 20 Feb. 1699, and it is probable that Simson accompanied him, though he is not entered in the list of students. Never robust in health, he obtained no ministerial charge till 1705, when he was called to Troqueer, Kirkcudbrightshire on 21 June, and ordained there on 20 Sept. In 1708 he was promoted to be professor of divinity in Glasgow university, succeeding James Wodrow, father of the historian, Robert Wodrow [q. v.] He lectured in Latin, using Marck's ‘Medulla’ as his main text-book.
Throughout the last century Simson's name was a byword as a disseminator of unsound doctrine; but he seems to have been perfectly sincere in expressing his loyalty to the standards of his church; he retracted expressions interpreted by others in an heretical sense, and was never convicted of heresy. He had adopted the maxim that reason is ‘fundamentum theologiæ,’ and his aim was to make orthodoxy intelligible. During twenty years the ranks of presbyterian clergy in the west of Scotland and north of Ireland were recruited from his pupils.
As early as 1710 Simson discussed his views at Moffat with James Webster (1659–1720), minister of the Tolbooth church, Edinburgh, ‘a man of great warmth, but a narrow spirit’ (Calamy, Own Life, 1830, ii. 179). Subsequently he stated his position in correspondence with Robert Rowan (1660–1714), minister of Penningham, Wigtonshire, and with James Hog [q. v.], editor of ‘The Marrow.’ Webster first publicly attacked Simson in August 1712. On 17 March 1714 he made formal charges in the Edinburgh presbytery. Through the synod of Lothian the matter reached the general assembly, and Webster, acting under the assembly's order, tabled his complaint before the Glasgow presbytery in the autumn. Simson gave in his replies on 29 March 1715, and the general assembly on 8 May referred the case to a committee of thirty ministers and six elders, on 13 May. At the head of the committee was William Carstares [q. v.], who died before the end of the year. The ablest theologians upon it were James Hadow [q. v.], and William Hamilton, D.D., professor of divinity at Edinburgh, and grandfather of Bishop Horsley. The gist of the accusation was that Simson had attributed too much to the light of nature, but there were miscellaneous charges, e.g. he held it probable that the moon was inhabited. At the assembly of 1716 the ‘marrow-men’ clamoured for his suspension, but the case was deferred till the next assembly, when Webster broke out (8 May 1717) with what Wodrow calls ‘a dreadful sally.’ At the next sitting he apologised. On 14 May 1717 the assembly found that Simson had ‘vented some opinions not necessary to be taught in divinity,’ and had employed expressions ‘used by adversaries in a bad and unsound sense;’ these were prohibited for the future, but no further censure was passed. The assembly was, in fact, between two fires. On the same day judgment was given against the ‘Auchterarder creed’ [see Boston, Thomas, the elder]. Preaching at the outer church, Glasgow, on 19 May, Simson gave offence by allusions to his opponents ‘and even the magistrates.’
Eight years later his orthodoxy on the point of our Lord's deity was impeached. He admitted changes in his treatment of the topic. Up to 1722 he had taken John Owen, D.D. [q. v.] , as his model; for two years (1723–4) he had specially controverted the semi-Arian teaching of Samuel Clarke (1675–1729) [q. v.]; finding that this course had its dangers, he began in December 1725 to combat the opposite error of Sabellianism, and was in consequence accused of going over to Samuel Clarke. He defended his procedure by affirming his judgment that, in the then state of Scottish theology, there was danger of Sabellianism and Socinianism, none of Arianism. His own account is closely confirmed by the evidence of his students. On 16 Feb. 1726 Charles Coats, minister of Govan, brought the matter before the Glasgow presbytery, who drew up six queries, which Simson declined to answer. Delay was caused by the state of Simson's health. Wodrow thought him ‘in a dying condition,’ and that his disorder had affected his head, for he brought in ‘Clarke, the Fathers and the Council of Nice in all conversations.’ He was unable to attend the assembly of 1726. On 18 May 1727 the assembly suspended him till the next assembly, and appointed a committee of twenty-one ministers and ten elders to co-operate with the Glasgow presbytery in preparing the case. On 16 May 1728, after receiving Simson's explanations and withdrawals, the assembly found his sentiments to be ‘sound and orthodox,’ but his teaching had been ‘subversive,’ and his explanations tardy. He was suspended till another assembly should take off the sentence; meantime the matter was to be referred to the presbyteries. Charles Owen, D.D.