"When I endeavour to examine my own conduct, when I endeavour to pass sentence upon it, and either to approve or condemn it, it is evident that, in all such cases, I divide myself, as it were, into two persons, and that I, the examiner and judge, represent a different character from that other I, the person whose conduct is examined into and judged of. The first is the spectator, whose sentiments with regard to my own conduct I endeavour to enter into, by placing myself in his situation, and by considering how it would appear to me when seen from that particular point of view. The second is the agent, the person whom I properly call myself, and of whose conduct, under the character of a spectator, I was endeavouring to form some opinion. The first is the judge; the second the pannel. But that the judge should, in every respect, be the same with the pannel, is as impossible, as that the cause should, in every respect, be the same with the effect."
— Smith, Adam (1723-1790)
(p. 202; cf. p. 113 in Liberty Fund ed.)
Text from The Theory of Moral Sentiments. By Adam Smith, Professor of Moral Philosophy in the University of Glasgow. 2nd ed. (London: Printed for A. Millar, in the Strand; and A. Kincaid and J. Bell, in Edinburgh, 1761). <Link to ESTC><Link to Google Books>
Reading Adam Smith, The Theory of Moral Sentiments, ed. D.D. Raphael and A.L. Macfie (Indianapolis: Liberty Fund, 1984).