After studying at St Andrews, Glasgow, and Edinburgh, he was licensed as a preacher; but having failed to obtain a presentation to one of the churches in St. Andrews, he was shortly afterwards appointed professor of logic in St. Salvator's College.
[1] In 1777 Watson published History of Philip II of Spain (London, 2 vols.)
Praised by Horace Walpole, it had publishing success: translated into French, German, and Dutch, it also reached a seventh edition by 1812.
At the time of his death he was working on a History of the Reign of Philip III: it was completed by William Thomson, and published in 1783 (London; revised editions 1808 and 1839; French translation 1809).
[1] John Stuart Mill, discussing his childhood reading, wrote, " ...but my greatest delight, then and for long afterwards, was Watson's Philip the Second and Third.