It is evident that there is a principle of connexion between the different thoughts or ideas of the mind, and that in their appearance to the memory or imagination, they introduce each other with a certain degree of method and regularity. In our more serious thinking or discourse this is so observable that any particular thought, which breaks in upon the regu- lar tract or chain of ideas, is immediately remarked and rejected. And even in our wildest and most wandering reveries, nay in our very dreams, we shall find, if we reflect, that the imagination ran not altogether at adventures, but that there was still a connexion upheld among the different ideas, which succeeded each other. Were the loosest and freest con- versation to be transcribed, there would immediately be observed something which connected it in all its transitions. Or where this is wanting, the person who broke the thread of discourse might still inform you, that there had secretly revolved in his mind a succession of thought, which had gradually led him from the subject of conversation. Among different languages, even where we cannot suspect the least connexion or communication, it is found, that the words, expressive of ideas, the most compounded, do yet nearly correspond to each other: a certain proof that the simple ideas, comprehended in the compound ones, were bound together by some universal principle, which had an equal influence on all mankind.
Though it be too obvious to escape observation, that different ideas are connected together; I do not find that any philosopher has attempted to enumerate or class all the principles of association; a subject, however, that seems worthy of curiosity. To me, there appear to be only three principles of connexion among ideas, namely, Resemblance, Conti- guity in time or place, and Cause or Effect.
That these principles serve to connect ideas will not, I believe, be much doubted. A picture naturally leads our thoughts to the original: the mention of one apartment in a building naturally introduces an enquiry or discourse con- cerning the others: and if we think of a wound, we can scarcely forbear reflecting on the pain which follows it. But that this enumeration is complete, and that there are no other principles of association except these, may be difficult to prove to the satisfaction of the reader, or even to a man’s own satisfaction. All we can do, in such cases, is to run over several instances, and examine carefully the principle which binds the different thoughts to each other, never stopping till we render the principle as general as possible. The more instances we examine, and the more care we employ, the more assurance shall we acquire, that the enumeration, which we form from the whole, is complete and entire.
Section Four: Sceptical Doubts Concerning the Operations of the Understanding, Part One introduces a new distinction. Just as there are two kinds of perceptions, there are two kinds of ‘objects of human reason’ or propositions.
- What are the two kinds of perceptions?
Some propositions (or declarative sentences, for our purposes) are relations of ideas (ROIs) and some are matters of fact (MOFs). These are objects of human reason or inquiry; not all of them are true. The distinction is based not on whether the proposition is true or not, but rather on what it would take to make the proposition true.
Section Four: Sceptical Doubts Concerning the Operations of the Understanding, Part One also makes use of two other principles, in addition to the Copy Principle
The Separability Principle (SP) says that any two distinct perceptions can, in thought, be separated. No matter how many times the taste of an apple accompanies the sight of an apple, I can still think of the one perception without the other.
The Conceivability Principle (CP) is familiar from Descartes’s Sixth Meditation: Of the
Existence of Material Things, and of the Real Distinction Between the Mind and Body of Man. and from Berkeley’s work. If a state of affairs is conceivable, what follows, according to the
As you read, note where Hume is employing CP, SP, and CPY. This will help you keep track of his argument.