Hume’s Enquiry Concerning Human Understanding
In 1748, Scottish Philosopher David Hume published his work, An Enquiry concerning Human Understanding. In it, he attacks “dogmatic rationalism,” the prevailing view of the time which argued that total knowledge of the world could be acquired through the faculty of reason. Famously known for his skepticism, Hume introduces an epistemology that makes it clear that certain facts we take for granted in the world cannot be logically proven. For example, we have no rational explanation whether we know the sun will rise tomorrow. In this post, we’ll go over the main points Hume makes in his Enquiry.
Two types of perception exist: Thoughts and Impressions. Impressions are lively perceptions that we experience in the world. For example, I might feel pain when I put my finger over a flame. Thoughts are reflections on perceptions. For example, I can reflect on the pain I felt when I stuck my finger over the flame. According to Hume, thoughts are less lively versions of impressions. What’s important is that all knowledge about the world stems from impressions and persist as thoughts.
We navigate the world using reason, and the object of reason can take two forms: Relations of Ideas and Matters of Fact. Relations of Ideas are purely logical and independent from experience. We can say 1 + 1 = 2 because the definition of the operators (plus and equals), and the numbers is encompassed in the language medium. Another example is “All bachelors are unmarried.” By giving this statement, we introduce nothing new into the world, but it is true given the aspects of the language in which it is formed.
Matters of Fact is knowledge concerning facts in the world. This particular knowledge results singly from Cause Effect associations. For example, the billiard ball A moved because billiard ball B collided with A. Ball B caused Ball A to move. Knowledge about the world is Matter of Fact knowledge, and the foundation upon which such knowledge rests is Causation. But Hume takes one step further: What is the foundation of experience that enables Causation to exist?
One of the primary objects of Hume’s work is to prove whether Causation exists or not. According to Hume’s epistemology, there must be some Impression associated with Causation. Otherwise, we could not say Causation exists. We see Ball B hit Ball A, and as a result, we see Ball A move. We conclude Ball B caused Ball A to move. But in no moment did we see the impression of causation that makes this fact certain.
How do we know that, in the future, Ball B will always cause Ball A to move. What if, when Ball B hits Ball A, Ball A stands still? What is it that makes it certain that Ball A will always move when caused by Ball B? According to Hume, we have no evidence that Causation exists, and therefore we must let it go as a means for understanding the world. This sounds a bit crazy: if we can’t prove causation to exist, then how do we know the future will resemble the past? In my past life, whenever I drink water, I become hydrated. But what if tomorrow that no longer works? Causation requires the future to resemble the past. And according to Hume, we have no proof to justify this claim.
Instead, Hume believes “Causation” exists insofar as it is due to constant conjunction. In other words, in the past, every time I drank water, I became hydrated. Given the past circumstances, the probability that I will be hydrated the next time I drink water is 100%. But, we don’t come to understand this by reason: we come to understand it by habit. Reason, Hume believes, oversteps its bounds when it attempts to account for phenomena in the world via Causation. It is not some causal force that makes me hydrated, but instead, I develop a habit, or custom, that enables me to understand that, when I am thirsty, I should drink water.
Habits are not rational. Children and animals both learn experience in the world, and both lack reason to account for it. They learn by custom. They do not act because the act in concert with the metaphysical arrangement of causation, but because they come to understand through repetition that certain ways of engagement the world have certain outcomes.
Our belief in causation, according to Hume, is an artifact of dogmatic rationalism. Such views ask new questions that no longer makes sense, such as “Do I have Free Will?” Free will and determinism presuppose the notion of causation as a metaphysical idea. Thus, in Hume’s famous words:
Does it contain any abstract reasoning concerning quantity of number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: For it can contain nothing but sophistry and illusion.
