This thesis investigates Hume’s philosophy of external existence in relation to, and within the context of, his philosophy of scepticism. In his two main works on metaphysics – A Treatise of Human Nature (1739–40) and the first Enquiry (first ed. 1748) – Hume encounters a predicament pertaining to the unreflective, ‘vulgar’ attribution of external existence to mental perceptions and the ‘philosophical’ distinction between perceptions and objects. I argue that we should understand this predicament as follows: the vulgar opinion is our (...) natural and default belief for Hume, but causal reasoning reveals it to be false, and the philosophical alternative is a confabulation that we cannot permanently believe and is devoid of justification. Hume uses the fact that we cannot have a satisfactory account of belief in external existence as a sceptical consideration to motivate his wider philosophical scepticism. Hume’s response to his predicament about external existence is found in the context of his confrontation with other sceptical worries (Treatise 1.4.7 and Enquiry 12), in which Hume also reflects generally on the nature and implications of scepticism. I argue that we should characterise Hume’s position as residually sceptical. This means that, while Hume accepts the unanswerability of some sceptical problems, he denies that it is possible to eradicate all belief as a result (and denies that it is practically useful to even try) and instead uses sceptical problems as a motivation to adopt a moderately sceptical position. While we inevitably return to entertaining the vulgar belief, there is no solution to the sceptical predicament; Hume does not endorse the vulgar belief, or the philosophical system, or indeed any alternative system of the external world that might extinguish the predicament. Sceptical doubt, for Hume, does not derail intellectual pursuits, but rather modifies our attitudes in those very pursuits. (shrink)