John Stuart Mackenzie (1860–1935) was a British philosopher, born near Glasgow, and educated at Glasgow, Cambridge,[1] and Berlin. In 1884-89 he was a fellow at Edinburgh and from 1890 to 1896 fellow of Trinity College, Cambridge. He lectured on political economy at Owens College, Manchester, in 1890-93, and in 1895 became professor of logic and philosophy in University College, Cardiff. Mackenzie was an idealist philosopher and a Hegelian of the type of Green, Bradley, Bosanquet, and Caird.
Mackenzie was not religious and was subscribed to a humanist ethical belief system. He was a member of the Union of Ethical Societies (today's Humanists UK) since its founding meeting in 1896. He became the organisation's first official President in 1918.