Fergusson was an able, sober, scholarly young man of high moral character and attractive, if somewhat humourless, personality. On succeeding to his paternal estates he, like his close friend George Dempster, became ambitious of entering Parliament, and by the end of 1759 was the Argyll candidate for Ayr Burghs in opposition to Patrick Craufurd, supported by Bute. His success seemed assured until, in the new reign, Argyll and Bute composed their quarrel and agreed to sponsor a candidate acceptable to them both. Fergusson’s refusal to withdraw embarrassed Argyll, and enraged Eglintoun and other Bute supporters against ‘that absurd boy’,
In Parliament Fergusson, although in general a Government supporter, showed a certain independence. In his first recorded speech, 26 Oct. 1775, he advocated strong measures against America, urging that in defence of the authority of Parliament all party divisions should be laid aside; but on 24 Nov., as a strict constitutionalist, insisted that the Government must seek indemnity for sending Hanoverian troops to Gibraltar and Minorca without consent of Parliament.
Fergusson voted against Administration, 12 Feb. 1779, on the contractors bill, and also on 3 Mar. over Keppel. He spoke on 8 Mar. in support of the bill for the relief of Protestant Dissenters, contrasting the toleration allowed Episcopalians in Scotland with that of Presbyterians in England. Thereafter he intervened more frequently in debate; opposed, 26 Mar., Hartley’s motion to refuse money for army extraordinaries, while advocating a committee to consider better methods of dealing with public accounts; supported the bill to prevent adultery, 4 May 1779; and caused the Government some embarrassment on 2 July 1779 by raising the constitutional issue of whether the Lords had any right to amend a militia bill which, he maintained, was essentially a money bill.
In a rare intervention in a major American debate he opposed on 17 June 1779 Cavendish’s motion for concentrating all available forces against France and thereafter does not appear to have wavered in his loyalty to Administration. He spoke on 22 Mar. 1780 in defence of William Fullarton after his duel with Shelburne, opposed Crewe’s bill for disfranchising revenue officers, 13 Apr., and warmly justified concessions to Scotland on the malt tax.
At the general election Fergusson’s claim to independence was scorned by Sir Lawrence Dundas, who asserted he was ‘as hackney a ministerial Member as ever went from Scotland’.
Having already shown concern about the government of India and submitted plans to North for its reform,
I thought it my duty to the King to acquire for his service so able and respectable a man as Sir Adam Fergusson, and I think it my duty to Sir Adam to do everything in my power to prevent his being involved in difficulties ... I should therefore feel it as the most sensible obligation if you and your noble friends will permit Sir Adam to be re-elected upon this occasion without opposition.
Similar letters to Eglintoun and Cassillis resulted in the reluctant withdrawal of Montgomerie, and on 16 Aug. Sir Adam was returned unopposed. His tenure of office was brief, but from 25 Jan. 1782 he was assiduous in attendance at the Board until its last meeting on 1 May.
A silent supporter of North until his fall, Fergusson under the Rockingham Administration confined his contributions in debate to such matters as the effect on Scotland of the turnpike tax bill, the prohibition of home grown tobacco, and the new soap duties. In Indian affairs he continued active on the secret committee, unsuccessfully opposed on 24 Apr., with his friends Dempster and Pulteney, the select committee’s resolution to censure Laurence Sulivan; and was righteously indignant when the East India Company rejected the Commons resolution for the recall of Warren Hastings.
Under the Shelburne Administration he took a line over the peace treaty independent of Dundas; pleaded the cause of the loyalists and supported the motion for copies of the instructions given to Richard Oswald concerning them. He did not vote in the division of 18 Feb. but on 21 Feb. declared his view that the King had gone further than he had any authority to do by ceding part of Quebec and Nova Scotia to the Americans.
Under the Coalition he remained for a time apparently uncommitted; spoke frequently in the budget debates in support of Scottish interests, and while professing impartiality on the question of the tellership of the Exchequer granted to Dundas’s friend Chancellor Thurlow, ‘reasoned shrewdly’ on 7 July 1783 that it was unjust to include his office in the projected Exchequer reforms. He supported Lord John Cavendish’s motion for a new commission to inquire into loyalist claims, but feared lest if Parliament gave relief the Americans might evade their obligations under the peace treaty.
His views were undoubtedly influenced by his friendship with Dundas, whom he eventually followed into opposition, voting against Fox’s East India bill, 27 Nov. 1783. On the dismissal of the Coalition he supported Pitt; condemned on 27 Feb. the obstructive tactics of the Opposition, and on 5 Mar. attacked Fox for delaying the passage of the mutiny bill.
At the general election Fergusson was again opposed by Montgomerie and, after negotiations between Dundas and the Ayrshire peers, decided to withdraw under an agreement that he should represent the county in the following Parliament and meanwhile be returned for a safe seat. Dundas duly arranged the retirement of James Hunter Blair from Edinburgh City and secured the seat for Fergusson in August 1784.
While his connexion with Dundas gave him a certain importance, he received no office. He voted 18 Apr. 1785 for parliamentary reform, and for Pitt’s Irish propositions; but his rare speeches were concerned mainly with questions of parliamentary procedure, election and Scottish affairs. His legal arguments in favour of hawkers and pedlars, of a reduction in the coal tax, of the Scottish malt distillery, were ‘able and ingenious’, but only on such questions did he venture to disagree with Administration.
On the Regency question he voted, 16 Dec. 1788, with Administration, but in January 1789 on at least one occasion divided with Opposition. His bitter enemy, James Boswell, wrote, 23 Jan.:
He died 25 Sept 1813.
