David Hume, answered from the texts and cited to the page.
When I look inward as carefully as I can, I never find a self apart from particular perceptions; I find heat or cold, pleasure or pain, light or shade, love or hatred.1 The self is not an object of experience over and above the perceptions; it is "nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement." The sense of personal identity is produced by the smooth and uninterrupted progress of these perceptions through resemblance and causation, not by any continuing substantial self that underlies them.2345
The Appendix to the Treatise records honest dissatisfaction with this account: I cannot make the bundle theory cohere with my account of the principles of association that are supposed to do the unifying work. Whether the account can be repaired is a question I leave honestly open in the Appendix; what I do not retract is the negative thesis: when I look inward, I do not find a continuing self apart from perceptions.
The strongest sensation, the most violent passion, say they, instead of distracting us from this view, only fix it the more intensely, and make us consider their influence on self either by their pain or pleasure.A Treatise of Human Nature, pp. 164–165
But farther, what must become of all our particular perceptions upon this hypothesis? All these are different, and distinguishable, and separable from each other, and may be separately consider'd, and may exist separately, and have no need of any thing to support their existence. After what manner, therefore, do SB 253 > Of personal identity > 1.4.6 they belong to self; and how are they connected with it?A Treatise of Human Nature, p. 165
Every idea is deriv'd from preceding impressions; and we have no impression of self or substance, as something simple and individual. We have, therefore, no idea of them in that sense. Whatever is distinct, is distinguishable; and whatever is distinguishable, is separable by the thought or imagination. All perceptions are distinct.A Treatise of Human Nature, pp. 399–400
These therefore must be the same with self; since the one cannot survive the other. Is self the same with substance? If it be, how can that question have place, concerning the subsistence of self, under a change of substance? If they be distinct, SB 634 SB 635 what is the difference betwixt them? For my part, I have a notion of neither, when conceiv'd distinct from particular perceptions.A Treatise of Human Nature, p. 400
'Tis, therefore, on some of these three relations of resemblance, contiguity and causation, that identity depends; and as the very essence of these relations consists in their producing an easy transition of ideas; it follows, that our notions of per- SB 261 SB 262 1.4.6 sonal identity, proceed entirely from the smooth and uninterrupted progress of the thought along a train of connected ideas, according to the…A Treatise of Human Nature, p. 170
One of the most influential moves in modern philosophy of mind and personal identity. Derek Parfit's Reasons and Persons (1984) developed a contemporary descendant of the bundle theory grounded in psychological continuity and connectedness. The contemporary debate runs between bundle theorists (Parfit and his followers) and defenders of a substantial or transcendental unity of consciousness (Galen Strawson among others). Hume's Appendix confession is itself a major scholarly puzzle: what exactly did Hume find dissatisfying, and is the dissatisfaction fatal to the bundle account or only to its specific Treatise formulation? The standard scholarly readings divide on whether the Appendix retraction is local or systematic.