This theory does not give morality 'a sufficiently deep foundation in the constitution of man on the character of God, and could not have stood against the assaults of Hume.

Like all active opponents of the new scepticism he felt it necessary to oppose the favourite theory of Locke, that all our ideas are derived from sensation and reflexion.

His eldest sister married Gavin Hamilton, bookseller and publisher in Edinburgh (also, it is believed, a member of the Airdrie family), whose eldest son was Robert Hamilton, professor of mathematics in Marischal College and University, Aberdeen, author of a treatise on the national debt.

[7] His granddaughter Margaret Balfour married Rev John Paul, minister of St Cuthbert's Church, Edinburgh and Moderator of the General Assembly in 1847.

In 1737 his sister Bridget Balfour (d. 1764) married Rev Neil McVicar, minister of St Cuthbert's Church, Edinburgh.

[8] In 1750 his niece Helen Balfour, married rev Thomas Scott, minister of South Leith Parish Church.