1601 Shakespeare, Hamlet i. iii. 78: 'to thine own self be true'

1690 John Locke, An Essay concerning Human Understanding ii. xxvii. §9: 'consciousness always accompanies thinking, and 'tis that, that makes every one be, what he calls self.'

1739 David Hume, A Treatise of Human Nature i. iv. §vi: '[selves] are nothing but a bundle or collection of different perceptions...nor is there any single power of the soul, which remains unalterably the same...The mind is a kind of theatre'

1818 John Keats, writing to Richard Woodhouse: 'As to the poetical character itself...it is not itself - it has no self. It has as much delight in conceiving an Iago as an Imogen.'

1826 Benjamin Disraeli, Vivien Grey i. x. 63: 'Self is the only person whom we know nothing about.'

1862 Herbert Spencer, First Principles i. iii. §20 (1875) 65: 'If, then, the object perceived is self, what is the subject that perceives? or if it is the true self which thinks, what other self can it be that is thought of?'

1909 G.K. Chesterton, Orthodoxy iii. 63: 'You cannot call up any wilder vision than a city in which men ask themselves if they have any selves.'