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 to the Mind. If we allow, that Belief is nothing but a firmer and stronger Conception of an Object than what attends the mere Fictions of the Imagination, this Operation may, perhaps, in some measure, be accounted for. The Concurrence of these several Views or Glimpses imprints its Idea more strongly on the Imagination; gives it superior Force and Vigour; renders its Influence on the Passions and Affections more sensible; and in a word, begets that Reliance or Security, which constitutes the Nature of Belief and Opinion.

Case is the same with the Probability of Causes as with that of Chance. There are some Causes, which are entirely uniform and constant in producing a particular Effect; and no Instance has ever yet been found of any Failure or Irregularity in their Operation. Fire has always burnt, and Water suffocated every human Creature: The Production of Motion by Impulse and Gravity is an universal Law, that has hitherto admitted of no Exception. But there are other Causes which have been found more irregular and uncertain; nor has Rhubarb prov'd always a Purge, or Opium a Soporific to every one, who has taken these Medicines. 'Tis true; when any Cause fails of producing its usual Effect, Philosophers ascribe not this to any Irregularity in Nature; but suppose, that some secret Causes, in the particular Structure of Parts,