1. Introduction: Hume and Kant

David Hume (1711—1776)

David Hume was born to a family from Berwickshire, which is near Edinburgh Scotland. He was educated at home until, at 11 years old, he went to the University of Edinburgh. He left Edinburgh at age 15 and began to study independently. It was then that he became interested in Philosophy and began to question his religious beliefs. As a young man he lived in Scotland, England and France. In 1739 and 1740 he published his three volume Treatise of Human Nature. Hume’s Treatise, which is now considered to be one of the great works of philosophy, was largely ignored at the time. Subsequent to the Treatise Hume published is two-volume Essays, Moral and Political. These were written for a general audience and were more popular than the Treatise. This success led Hume, in 1748, to publish the Enquiry Concerning Human Understanding (also known as the “first Enquiry”). The first Enquiry is a review of the key line of argument in Book I of Hume’s Treatise. It is written much more in the style of Hume’s Essay than that or the Treatise. It is a portion of this line of argument that I am going to have you learn.

After the publication of the first Enquiry Hume published the Enquiry Concerning the Principles of Morals and his Political Discourses. Both of these books were widely praised and were influential on the next generation of Scottish and English political and economic thinkers including Jeremy Bentham, Adam Smith, William Godwin, and Thomas Malthus.

Hume unsuccessfully sought a professorship at the University of Glasgow. He was unsuccessful in part due to his reputation for anti-religious views. He did gain employment as librarian of the Advocate’s Library in Edinburgh. While there he wrote much of his highly successful six-volume History of England (published from 1754 to 1762). He later wrote two works on religion The Dialogues Concerning Natural Religion and The Natural History of Religion. The Dialogues was, on advice from Hume’s friends, not published until after his death. Hume continued to publish and to be a controversial figure until his death. In his personal life he was a bon vivant, someone who loved life and the joyous living of his life. During one of his stays in Paris the woman of Paris came to call him “le bon David” (the good David) because he was so joyous and awkwardly charming.

Immanuel Kant (1724-1804)

Immanuel Kant, unlike David Hume, has a reputation for being anything other than a bon vivant. Kant was born in in the Prussian city of Königsberg (now Kaliningrad in Russia) and lived there his whole life. Kant attended the University of Königsberg where he later became a professor. Kant began his professorial career as a Cartesian Rationalist using the kind of rationalist philosophy that was widely accepted among German philosophers of his time. In the early 1770s, Kant discovered Hume’s skepticism. This discovery challenged the very foundations of Kant’s philosophical approach. Hume, Kant wrote, woke him from his “dogmatic slumber” and forced Kant to reevaluate his whole philosophical framework. Kant then made it his philosophical mission to respond to Hume’s skepticism. This became his life’s work as it required a fundamental reorientation of metaphysics and epistemology. After a decade of work this led to Kant’s publication of the epochal Critique of Pure Reason in 1781.

During the decade that followed the “first Critique” Kant published a series of major works that transformed much of how philosophy was approached. This included vitally important work in ethics that make Kant one of the most important moral philosophers.

Kant lived his whole life in Königsberg and, while he was not the bon vivant that Hume was, but rather a man of modest and regular habits, he was considered a good friend and was popular teacher. His influence was so great that during his lifetime he was called the “the sage of Königsberg.” At the time of his death he was so famous and highly regarded that his funeral was attended by thousands of people who came to pay him tribute.

Hume and Kant

The differences between Hume and Kant extend to many of the key areas of philosophical thought. These include differences regarding metaphysics, epistemology, ethics, and philosophy of religion. The difference between these two thinkers is so profound because of the difference in their fundamental philosophical orientation. Hume is a committed empiricist, following in the tradition defined by John Locke. Kant was of the view that Hume’s empiricism led to the dead end of skepticism. Skepticism is the view that it is impossible to have knowledge. Hume’s skepticism is the result of an extended argument that we cannot provide a rational justification for our knowledge claims. So-called knowledge is based on judgments that result from habit and natural inclination not rational justification. Hume admitted to his skepticism, calling it a “mitigated” or an “academical” skepticism. For Hume, skepticism is mitigated or academical because it only applies to philosophers (although, remember, at that time people we now call “psychologists” and “scientists” were considered philosophers) and other scholars. It in no way affects our quotidian existence. Hume’s core argument for this position is presented below.

Kant was deeply concerned by Hume’s skeptical conclusion. It was his view that we do in fact have knowledge. The success of science and the ambitions of philosophy both depend, Kant thought, on our ability to rationally justify our ideas. In this way his core impulse was very much like Descartes in responding to the intellectual upheavals of his time. Kant’s response to Hume was an attempt to reconstitute rationalism along lines very different from the Cartesian rationalism in which he was educated. This new “Kantian rationalism” is explained in the section on Kant.

The division between Kantian and Humean thinkers continues today. Contemporary empiricism is often derived from Hume and rationalism from Kant. While in the 220 some years since Kant’s first Critique there have been many vitally important innovations in philosophical thought (some of which we will review in the last few weeks of the semester), understanding the split between Hume and Kant is the basis for understanding the core claims of later philosophers.

2. Hume and his Fork

Hume divides all mental awareness into two categories. These are impressions and ideas. Impressions are sensations of the outer world or feelings of our inner world. So, for example, in walking in the rain one might have the sensation of feeling damp. Or, in reading Hume, one might have the feeling of frustration. Ideas, Hume claims, are all copies of impressions. Ideas, Hume also claims, are less lively than impressions. The idea that reading Hume is frustrating is less lively or vivid than the feeling of frustration you felt when reading Hume.

Ideas are formed from impressions on the basis of memory or imagination. Memory is a more or less accurate copy, though weaker, of impressions. Imagination takes the basic ideas formed in memory and recombines them using three principles of association, namely, resemblance, contiguity, and cause and effect. Resemblance, contiguity, and cause and effect lead us to combine ideas into more complex ideas. For resemblance, you may see the same person acting in similar ways in different situations and, from this, you may form an idea of that person’s character. For contiguity, you may see two people together in a variety of different places and you think they are a couple. And then, after hearing that this couple argued and no longer seeing them together, you may conclude that the argument caused them to break up.

Imagination may lead us to combine ideas in fanciful ways such as imagining a winged horse. However, fancy, Hume claims, is different from understanding. Our fancies are the product of desire or the wanderings of our thoughts. They do not reflect the actual experience of the world. Understanding, on the other hand, is the product of reason or enquiry. It is in the exposition of the operation of the understanding that Hume’s distinctive contribution to epistemology is presented.

In Section IV of his An Enquiry Concerning Human Understanding Hume writes, “the objects of human reason or enquiry may naturally be divided into two kinds, to wit, Relations of Ideas, and Matters of Fact.” Hume goes on to explain that Relations of Ideas are those “affirmations” that are “either intuitively or demonstratively certain.” He also says that “Propositions of this kind are discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe.” Regarding Matters of Fact, Hume explains that they cannot be known through reason alone and that the “contrary of every matter of fact is still possible”. Such assertions are never demonstratively certain and our knowledge about them is always based on experience. Reasoning about matters of fact is “founded on the relation of cause and effect.”

This distinction between relations of ideas and matters of fact is called Hume’s Fork because, like a fork, it has two tines.

So, for example, circles contain no straight lines, 2 2=4, or the Pythagorean theorem, are relations of ideas. The first of these is intuitively certain. The second and third can be proven, given certain assumptions, but these assumptions are typically taken as intuitively certain. These later two are demonstrations based on what is intuitively certain. Reasoning about relations of ideas is often called “reasoning a priori.” “A priori” is understand as without experience. More on this with Kant.

“I get damp when it rains” or “the sun in March feels nice” are claims about matters of fact. In both cases we can imagine the contrary as being the case. They are not necessarily true. Reasoning about relations of ideas is often called “reasoning a posteriori.” “A posteriori” is understand as with or on the basis of experience.

Because relations of ideas are “without dependence on what is anywhere existent in the universe” they do not tell us anything about the way world is. They simply tell us about how we must think about the world. Only our understanding based on matters of fact is informative about the world.

3. The implications of Hume’s Fork

Cause and effect

Causal reasoning is fundamental to our understanding of how the world works. We negotiate our way though life by concluding that if I do such and such, that will lead to so and so happening.

Hume argues that connection between cause and effect is not “attained by reasonings a priori.” Therefore, it must be a matter of fact, only knowable through experience. However, Hume argues that in our experience “every effect is distinct from its cause” and that the apparent conjunction between one event and another must appear to be “arbitrary”. Due to this any notion of causation that goes beyond our particular experience of a “constant conjunction” between two events leads us only to the recognition of human ignorance. Think about throwing an object in the air. Most of the time it will fall to the ground. (What if it is a helium balloon? A healthy bird?) What does this tell us about cause and effect? Hume claims it tells use nothing other than that, most of the time, when an object is thrown in the air it falls to the ground. This is what Hume means by “constant conjunction.” It does not show us that throwing the object in the air causes it to fall to the ground. It does not show us that it falls because of gravity. It simply shows us that one event typically follows another. All so-called “causation” is, empirically, mere correlation. The occurrence of one thing is accompanied the occurrence of another.

Hume concludes from this that reasoned justification of “These ultimate springs and principles are totally shut up from human curiosity and enquiry.” Causal connection, has no basis in our experience of things. It is merely a connection we come to feel as we expect events that have been to conjoined to be conjoined in the future. It is a habit of anticipation. “Cause” is, therefore defined as “an object followed by another, whose appearance always conveys the thought to that other.”

However, Hume goes on to argue, in Section V of his Enquiry, that in spite of the skeptical conclusions a rigorous philosophy leads us to, “Nature will always maintain her rights, and prevail over any abstract reasoning whatsoever.” “Custom, then, is the great guide to human life. It is that principle alone, which renders our experience useful to us and makes us expect, for the future, a similar train of events with those which have appeared in the past.” Philosophy guides us to the limits of philosophy. At these limits, the limits Hume’s empiricism takes us to, we need to give up philosophy and acknowledge the limits of our knowledge.

Further implications of Hume’s Fork

Hume extends the empiricist argument against our rational knowledge of cause and effect to other core philosophical beliefs. He argues that we cannot justify our reliance on inductive inference because it depends on the assumption of the uniformity of nature or that the future will resemble the past. Furthermore, we have no evidence that we have free will. All we know is that when we want something then we sometimes act so as to get what we want. We have no experience of a self or soul. We simply see the resemblance of body has to itself at different times and have vague memories of connections between our various thoughts and experiences. The external world is simply a set of ideas in our mind. We have a “vulgar belief” that things are real outside of our thoughts, but we can give no philosophical justification for it. The “vulgar belief” is so firmly held, however, that the philosophical realization that it is not a justified belief has no effect on our firm conviction that there is such a world. That conviction is wound up with everything we do and say. Someone who denied it would be labeled insane. But that does not justify the belief.

And, similarly, there is no evidence for god or any kind of divine being. We cannot use reason alone (as in the ontological argument) to argue for the existence of god because the definition of god as a necessary being is simply a relation of ideas and relations of ideas can tell us nothing about the world. And, of course, cosmological arguments will not work because cosmological arguments depend on the concept of causation which, Hume has argued, cannot be rationally justified.

If Hume is correct, this also means that, in terms of Descartes’ Meditations on First Philosophy, we are stuck at the cogito stage of the argument. I know I exist when I think about my existence. I can know the truths of mathematics and geometry. Beyond this, however, it would seem that all my so-called knowledge is subject to skeptical doubt.

Hume’s academic or mitigated skepticism

So, Hume concludes:

“If we take in our hand any volume—of divinity or school metaphysics, for instance—let us ask, Does it contain any abstract reasoning about quantity or number? No. Does it contain any experiential reasoning about matters of fact and existence? No. Then throw it in the fire, for it can contain nothing but sophistry and illusion.”

Hume is arguing that, for the most part, we cannot rationally justify our most fundamental beliefs. This is, in Hume’s view, one of the key conclusions a rigorous empiricism leads us to. Hume’s empiricism, if correct, should also serve as a warning to not try to do too much with philosophy. We should realise that we cannot prove things, like the existence of god, that we have no impressions of. What, a follower of Hume would ask, impression gave you the idea of god? And we certainly cannot use god, and the belief that god is no deceiver, to claim to prove things such as the existence of a world outside of our mind or the supposed fact that I exist as both mind and body. While each of us has firm beliefs about these things, Hume argues, belief is not the same as knowledge or reasoned understanding.

In this way Hume is a skeptic. He believes that much of what we claim to know is not rationally justifiable. It is firm belief. But we do not have the ability to know whether such beliefs are true. This is because experience does not provide reason with the tools it needs to justify such beliefs.

However, Hume also claims, at least in his Enquiry, that his skepticism is a mitigated or academical skepticism. This is because although I cannot, for example, justify my inferences employing cause and effect, I cannot help but make such inferences. We do this through habit and instinct. Philosophy cannot change this. We will continue to act on assumptions that cannot be rationally justified. This, again, does not mean that such assumptions are true. It merely means that we cannot help but believe in them. This is sometimes called Hume’s skeptical solution to the problem of skepticism.

Now, having done this reading, watch the following videos where Professor Daniel Greco explains Hume’s fork and applies it to two other of our fundamental beliefs:

(1) the reliability of induction and

(2) the uniformity of nature.

 

(The videos are also available at http://www.wi-phi.com/video/humes-skepticism-part-1 and http://www.wi-phi.com/video/humes-skepticism-part-2)