[2] He was educated at the Independent College in Taunton, Regent's Park College, at the University of Göttingen, where he studied under Hermann Lotze, and at the Humboldt University of Berlin, where he studied under Emil du Bois-Reymond and Hermann von Helmholtz.

[3] Sully was originally destined for the nonconformist ministry and in 1869 became classical tutor at the Baptist College, Pontypool.

Between 1892 and 1903, he was Grote Professor of the Philosophy of Mind and Logic at University College London, where he was succeeded by Carveth Read.

[5] An adherent of the associationist school of psychology, his views had great affinity with those of Alexander Bain.

Sully wrote monographs on subjects such as pessimism, and psychology textbooks, some of the first in English, including The Human Mind (1892).