We need only reflect on what has been prov'd at large, that we are never sensible of any connexion betwixt causes and effects, and that 'tis only by our experience of their constant conjunction, we can arrive at any knowledge of this relation.
David HumeWe may well ask, What causes induce us to believe in the existence of body? but 'tis vain to ask. Whether there be body or not? That is a point which we must take for granted in all our reasonings.
David HumeUpon 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 thought to pass from cause to effects and effects to causes, according to their experienc'd union.
David Hume