[3][4] Hew Scott states that it is "not unlikely" that his father was George Rule, minister at Longformacus, and his mother, Anna Johnston.
[5] After a distinguished career at the University of Glasgow, where he was regent, he became (at an unusually early age), Sub-Principal of King's College, Aberdeen, in 1651.
Before the trial Orde died by a fall from his horse at Ovingham, Northumberland, and, in the absence of a prosecutor, Rule was acquitted.
He returned to Scotland, preached for a time in Fife, but incurring the displeasure of the Privy Council, fled to France and Holland.
[10] At Linton Bridge, near Prestonkirk, Haddingtonshire, Charles Hamilton, 5th Earl of Haddington, fitted up for him a meeting-house, which was indulged by the privy council on 18 December 1679.
Gilbert served as minister to the presbyterian congregation of Wood Street Church, Dublin from 1682 until 1687, as a colleague of Daniel Williams.
Rule in the meantime had been in London, to forward the Presbyterian interest, and had gained the special notice of William III.
His predecessor as Principal, Dr Alexander Monro had been ejected for not taking the oath of allegiance to William and Mary, and wrote a work in defence of his faith called "An Enquiry into the New Opinions (chiefly) Propagated by the Presbyterians of Scotland; Together with some Animadversoins on a Late Book entitled 'A defense of the Vindications of the Kirk'; in a Letter to a Friend at Edinburgh".