[2] Fergusson was elected as the Member of Parliament for Sutherland in 1734, and sat for that county until he was made lord of session on 7 November 1735.
[4] In Tytler's Life of Lord Kames Fergusson is estimated as "undoubtedly one of the ablest lawyers of his time.
His knowledge was founded on a thorough acquaintance with the Roman jurisprudence, imbibed from the best commentators of the pandects, and with the recondite learning of Craig, who has laid open the fountains of the Scottish law in all that regards the system of feudalism.
… The decisions which he has recorded during the period when he sat as a judge of the supreme court exhibit the clearest comprehension and the soundest views of jurisprudence, and will for ever serve as a model for the most useful form of law reports".
[5] In September 1726 Fergusson married, Jean (1703–1766) (daughter of James Maitland, Viscount Maitland (born circa 1680–1709) and Jean, daughter of John Gordon, 16th Earl of Sutherland).