and papers, present themselves in the same uniform manner, and change not upon account of any interruption in my seeing or perceiving them. This is the case with all the impressions, whose objects are suppos'd to have an external existence; and is the case with no other impressions, whether gentle or violent, voluntary or involuntary.
This constancy, however, is not so perfect as not to admit of very considerable exceptions. Bodies often change their position and qualities, and after a little absence or interruption may become hardly knowable. But here 'tis observable, that even in these changes they preserve a coherence, and have a regular dependence on each other; which is the foundation of a kind of reasoning from causation, and produces the opinion of their continu'd existence. When I return to my chamber after an hour's absence, I find not my fire in the same situation, in which I left it: But then I am accustom'd in other instances to see a like alteration produc'd in a like time, whether I am present or absent, near or remote. This coherence, therefore, in their changes is one of the characteristics of external objects, as well as their constancy.
Having found that the opinion of the continu'd existence of body depends on the coherence and constancy of certain impressions, I now proceed to examine after what manner these qualities give rise to so extraordinary an opinion. To begin with the coherence; we may observe, that tho' those internal impressions, which we regard as fleeting and perishing, have also a certain coherence or regularity in their appearances, yet 'tis of somewhat a different nature, from that which we discover in bodies. Our passions are found by experience to have a mutual connexion with and dependence on each other; but on no occasion is it necessary to suppose, that they have existed and operated, when they were not perceiv'd, in order to preserve the same dependence and connexion, of which we have had experience. The case is not the same with relation to external objects. Those require
a continu'd existence, or otherwise lose, in a great