Hume and Moral Philosophy
Hume speaks of “moral philosophy” in the very beginning of his treatise. I have a sneaking suspicion that one of the main purposes of his writing is to overthrow moral philosophy and religion up till his time, like what Nietzsche attempted a century later. Hume didn’t come right out and attack Christian philosophy, perhaps because blasphemy law was still in effect in the U.K.
Epistemology and ethics are closely related branches of philosophy. In Plato, epistemology is the foundation of ethics. Unless we know what is good concerning the nature of man, we cannot live a good life. Hume is keenly aware of this, which I think is why he focuses on epistemology, to “undermine the foundations of an abstruse philosophy”, i.e., the “superstition” of the “moralists”.
Incidentally, I think both Plato are Hume are consistent in this regard, whereas Kant is not. Kant advocates ethics on the one hand, while denying that knowledge of human nature is possible on the other.
Devoid of Substance
With the abovementioned purpose in mind, Hume dismisses the notion of essence or substance in classical philosophy, by subtly excluding it entirely from his propositions. I didn’t notice something is amiss, until Hume put down the following challenge to rationalists:
“These two propositions are far from being the same, I have found that such an object has always been attended with such an effect, and I foresee, that other objects, which are, in appearance, similar, will be attended with similar effects…. The connexion between these propositions is not intuitive. There is required a medium, which may enable the mind to draw such an inference, if indeed it be drawn by reasoning and argument. What that medium is, I must confess, passes my comprehension; and it is incumbent on those to produce it, who assert that it really exists,”
Hume is right that the inductive argument is a non sequitur, i.e., objects which are similar in appearance don’t necessarily produce similar effects, and he challenges rationalists to provide “the medium”, i.e., another premise that would make the inference necessarily true.
What is missing from the argument is the philosophical concept of essence, which would make the logical connection clear. Essence is by definition what necessarily makes a thing what it is. For example, the essence of bread includes its power as food to nourish. However, essence is not observable by the senses but only arrived at by abstraction, and is commonly used by the scholastic philosophers against whom Hume has an axe to grind. So he excludes it from discussion.
Premise 1: An object of certain essence is always attended with such an effect,.
Premise 2: Objects with certain attributes in appearance are all of this essence.
Conclusion: Objects with certain attributes in appearance will be attended with the same effects.
Nature has kept us at a great distance from all her secrets, and has afforded us only the knowledge of a few superficial qualities of objects; while she conceals from us those powers and principles on which the influence of those objects entirely depends.
I can agree with Hume that the more we think about concepts like cause and effect, the more we realize that we don’t know the cause. Humility is the likely outcome of such thought.
We don’t know what causes things to be what they are today, and so we can’t deduce what they will be tomorrow. From the fact that the sun rises today, it doesn’t necessarily follow that it will rise tomorrow.
By the same token, however, Hume’s own proposition that ideas are derived from the senses does not stand up to scrutiny either. We don’t know what causes ideas to form in our minds. From the fact that there are similarities between objects of the senses and the ideas in our minds, or that sensory experiences come before the formation of ideas, it does not follow that the former are the cause of the latter, or that the latter are derived from the former.
Hume undermines his own philosophy with his skeptical denial of causal relationships.
Cause and Effect
Hume examines how logic works, and questions whether our logical inferences are valid. He analogizes causal relations between two associated ideas to a physical movement between two points on a line. First, the space between the two points is almost infinitely divisible, therefore the causal movement is almost impossible. Second, just because two events follow each other in spacetime, it doesn’t mean that one is the cause of another. IOW, succession or correlation is not causation.
To my mind, Hume’s notion of cause is encapsulated in Aristotle’s notion of “essence”, i.e, that which necessarily causes a thing to be what it is. However, being able to define something, is not the same as possessing its power. For example, being able to define life is not the same as possessing the power of creating and subsisting life. It is the latter to which Hume assigns cause proper, and as such, causes are “secret springs and principles”, and not known by us from any experience.
Hume makes two main propositions:
First, the cause and effect relations that people commonly observe and experience are not cause and effect proper.
Second, ideas are derived from or based on experiences, without exception, including the ideas of cause and effect.
There is a self-contradiction here: If the cause and effect relations that we experience are not cause and effect proper, it follows that the idea of cause and effect proper is not based on experience. Hume should have reflected on his own thought process, and concluded that many ideas are not based on experience.