…tho’ this conclusion [that objects continue to exist unperceived] from the coherence of appearances may seem to be of the same nature with our reasonings concerning causes and effects … they are at the bottom considerably different from each other …. Since nothing is ever really present to the mind, besides its own perceptions, ‘tis not only impossible, that any habit shou'd ever be acquir'd otherwise than by the regular succession of these perceptions, but also that any habit shou'd ever exceed that degree of regularity. Any degree, therefore, of regularity in our perceptions, can never be a foundation for us to infer a greater degree of regularity in some objects, which are not perceiv’ d; since this supposes a contradiction, viz. a habit acquir'd by what was never present to the mind. But ‘tis evident, that whenever we infer the continu'd existence of the objects of sense from their coherence, and the frequency of their union, ‘tis in order to bestow on the objects a greater regularity than what is observ'd in our mere perceptions .... as all [causal] reasoning concerning matter of fact arises only from custom, and custom can only be the effect of repeated perceptions, the extending of custom and reasoning beyond the perceptions can never be the direct and natural effect of the constant repetition and connexion, but must arise from the co-operation of some other principles. (pp. 197–8)