In David Hume's AN ABSTRACT OF A BOOK lately PUBLISHED; ENTITULED, A Treatise of Human Nature, &c, he reflects on a larger work concerning the "secret tie or union among particular ideas, which causes the mind to conjoin them more frequently together, and makes the one, upon its appearance, introduce the other" (pg 11; 34).
Hume uses the example of two billard balls hitting each other to help illustrate the notion of cause and effect, which becomes the foundation for every conceivable train of thought that our minds engage in. Hume states that it is only through our experience that we are able to conceive thought, and says, "TIS not, therefore, reason, which is the guide of life, but custom. That alone determines the mind, in all instances, to suppose the future conformable to the past"(pg. 6; 16). Essentially this means that it is impossible to use reason if we do not have any experience in a given situation, but does this mean that the human mind is incapable of improvising and constructing new ideas that seem all together unconnected from our past experiences?
In his example of the two billard balls hitting each other, Hume says that, "when I see a billiard-ball moving towards another, my mind is immediately carry’d by habit to the usual effect, and anticipates my sight by conceiving the second ball in motion. But is this all? Do I nothing but CONCEIVE the motion of the second ball? No surely. I also BELIEVE that it will move. What then is this belief? And how does it differ from the simple conception of any thing? Here is a new question unthought of by philosophers"(pg. 6; 17). Indeed, if one has never experienced a game of billards, then it would be very difficult if not impossible to conceive visually what will happen when the cue ball is struck into another ball.
Hume's idea of experience as the foundation for every connected thought or idea is strengthened when he states that, “secondly, THE mind has a faculty of joining all ideas together, which involve not a contradiction; and therefore if belief consisted in some idea, which we add to the simple conception, it would be in a man’s power, by adding this idea to it, to believe any thing, which he can conceive" (pg.6; 20). This statement clarifies the way in which Hume believes are minds operate, in that for a given situation, we essentially will fill in the blanks with imagination by drawing upon past experiences. If one is isolated from society and has little or no experience in their past, then it will be impossible for this person to ever unlock the ability to use reason or imagination.
