It seems most appropriate, before having any mention of Hume’s philosophy, to briefly enunciate the concept of empiricism. Prior to Immanuel Kant’s solicitation of Transcendental Idealism, the schools of epistemological thought were divided into rationalism and the aforementioned empiricism. The former is the belief that knowledge is innate, and that logic and reason are the chief methods of acquiring that knowledge. Conversely, empiricists believe that knowledge is sensory, or experience, based; in essence, that human beings are tabula rasa. It is upon the latter end of this dichotomic spectrum that we find Hume’s epistemology; that of empiricism.
Hume divides experiences, or perceptions, into two categories. The first is impressions, and the second is ideas. These are distinguished between one another, he says, by their respective degrees of force and vivacity; that is, how strongly these perceptions strike us, and how clearly they present themselves within our minds. “Those perceptions, which enter with most force and violence, we may name impressions; and under this name I comprehend all out sensations, passions and emotions, as they make their first appearance in the soul,” (Pg. 7, Paragraph 1). Here, we see that impressions come with the greatest amount of force and vivacity, and that they are comprised of our senses and nonphysical feelings. Before expanding on this, however, it would be beneficial to see what he has to say about ideas. “By ideas I mean the faint images of these [perceptions] in thinking and reasoning […]” (Ibid). Ideas, then, are the what is left over when an impression is removed.
I can clearly imagine this distinction by examining the book on the desk before me. It is paperback and bound in glue; its words have been typed in black ink upon white paper; its cover is of a distinct green. While I continue to stare at it, studying its myriad of details, the book continues to deliver to me powerful impressions, and it doesn’t take any effort to remind myself of those qualities that the book possesses because it remains in my gaze. Now, removing it from my sight, I am no longer receiving those impressions which made the book so vivid and strong in my mind. To envision it within my mind, I instead rely upon the fleeting ideas that I have of the book. Obviously, these are far less powerful and vivid when the object of my thoughts has been separated from my senses. It is in this manner that ideas are derived, or copied, from impressions.
Hume adds yet a further division to these perceptions, however, by enumerating what he calls simple and complex perceptions. The most readily understandable difference between these is nothing more than their respective divisibility. "Simple perceptions or impressions and...