Apprenticed to a local surgeon, and later educated at King's College, Aberdeen, from 1750 to 1755, he obtained his MA degree in 1753 and went on to continue his surgical training in London under Dr George Macaulay.

Having entered the Navy in 1757, Ramsay served as surgeon aboard HMS Arundel in the West Indies, under the command of Sir Charles Middleton.

In November 1759, the Arundel intercepted a British slave ship, the Swift and, on boarding the vessel, Ramsay found over 100 enslaved people living in the most inhumane conditions.

[2] One of their daughters, Margaret, (1766 – Newtown, Ireland, April 1839) married Robert Smith (1754 – Chatham, Kent, 2 July 1813), a Major in the Royal Marines.

This led him into involvement in local government, but he was the target of much antagonism and personal attack from the planters, who resented his interference, because of his measures to ameliorate the conditions of enslaved people.

He briefly rejoined the navy in April 1778, accepting a chaplaincy in the West Indies with Admiral Barrington, where he was engaged in intelligence gathering against the French.

[4] This was the first time that the British public had read an anti-slavery work by a mainstream Anglican writer who had witnessed the suffering of enslaved people on the West-Indian plantations.

Again he was severely challenged by the plantation owners in England who were threatened by his anti-slavery works and who attempted to refute his allegations, in many cases with vitriolic attacks on Ramsay's reputation and character, leading to a pamphlet war between the parties.