Abstract

In Book I of the Treatise of Human Nature, Hume examines the idea of necessary connection, which, he observes, forms an indispensable part of our idea of cause and effect. He concludes:The idea of necessity arises from some impression. There is no impression convey'd by our senses, which can give rise to that idea. It must, therefore, by deriv'd from some internal impression, or impression of reflexion. There is no internal impression which has any relation to the present business, but that propensity, which custom produces, to pass from an object to the idea of its usual attendant. This therefore is the essence of necessity. Upon the whole, necessity is something, that exists in the mind, not in objects; nor is it possible for us ever to form the most distant idea of it, consider'd as a quality in bodies. Either we have no idea of necessity, or necessity is nothing but that determination of the thought to pass from causes to effects and from effects to causes, according to their experienced union.