David Hume's Abstract for the Treatise on Human Nature

I recently finished a later work of the philosopher David Hume, an extended essay titled "Enquiry into Human Understanding", which in some ways soft-pedals the views he put forth in his well-known Treatise. What I found more interesting was the short abstract he wrote of his longer Treatise that was included in the collection. He summarizes his main arguments in such a clear way that I feel that I understand his other works better. It also strikes me how simple his main argument is, and also how seeing it presented so simply highlights the one philosophical opening which Kant later jumped upon -- the mention of "custom" being the motivation for the formation of our beliefs.

Hume starts from the perspective that all we know comes from our "perceptions" -- our ideas and our experiences. Then he argues that our ideas only come from our experiences. This includes our inner experiences, such as the feeling of an emotion or bodily sensations. We form our ideas by putting together various experiences, but it has to come from somewhere. He places ideas as being "weaker" perceptions in that they are never as vivid as the experiences from which those ideas are formed -- nothing is as real as reality.

He uses this basis to strike a sceptical blow to all philosophers claiming absolute knowledge. The basic argument is that we don't have any way of directly experiencing any of the basic principles that would allow us to have absolute knowledge in something. For instance, we can't experience "cause and effect" directly. We can see certain events leading to other events and see this repeated over and over, but this is only to show a predictive pattern. What we can't do is assume that this would continue ad infinitum into the future, because this assumes another principle we will never be able to experience directly, "constancy of physical law". We don't actually know that whatever patterns we see in this world will continue indefinitely -- we can only speculate reasonably based on what we have experienced in this world. We use these experiences to form reasonable working theories about our world, and those theories go all the way down to basic "laws" like cause and effect.

Theories and beliefs are very different, though -- a theory is a well-supported hypothesis, while a belief implies something much more certain. Hume argues that the main difference between a theory and a belief is emotional intensity. When we believe something we hold onto it more intensely and are less apt to question it. Most of our basic fundamental principles of thought are actually theories derived from experience, but they are so established that we treat them like absolute laws -- this treatment is due to the force of emotional attachment to these basic structures. Hume is a hard sceptic in this regard -- he insists that we treat even basic ideas like cause and effect as theories, and in general that we regard the limits to our own knowledge with a great deal of humility. In Hume's view, nothing is absolutely certain -- we live in a world of probabilities and working theories. This is why Hume is thought by many to be the father of modern philosophy -- he opened up the possibilities of modern pragmatism, deconstructionism and the like with his practical sceptical approach to epistemology.

He opened up the door to Immanuel Kant, who in some ways fathered modern psychology, by his comment on why people tend to treat things like cause and effect as absolute beliefs. Hume doesn't really answer this, instead saying that it is done because of "custom." But this opened up the question of why it is our custom. Kant's answer is that it has to do with the way we are built to perceive the world. Our minds are built to find patterns and form beliefs, Kant says. This is because there are basic principles that we are built to take for granted, like cause and effect, because that allows us to give structure and a working coherency to the world we see. Without assuming such things as cause and effect, we couldn't start to see patterns of cause and effect in our world -- we would just see a slew of data without any connections. While we may now disagree with Kant as to which basic principles are inborn, his insight was a big step towards psychology because it made us start to examine how it is that we process and organize our perceptions on the most basic operational level. Kant, in effect, opened up the can of worms that Hume's scepticism created.