He was educated abroad, but returned to Scotland as an adherent of the Prince of Orange, and represented Midlothian in the parliaments of 1700–2 and 1702–7.
[3] He was appointed an ordinary lord of session, on 1 November 1689, assuming the title of Lord Arniston, and sat on the bench for thirty years.
Guarini's Pastor Fido was among his favourite books.
[3] By his wife Margaret, daughter of Sir Robert Sinclair of Stevenson, he had four daughters and six sons, of whom the second, Robert Dundas the elder, became lord president of the court of session.
[3] His place as Senator of the College of Justice was filled by Hew Dalrymple, Lord Drummore.