Lecture 19 Humean Empiricism

Hume's Project (Enquiry 1)

Hume begins his Enquiry by distinguishing two manners of philosophizing. One manner, which we might call practical philosophy or etiquette (Hume doesn't give it a name), considers man chiefly as born for action , select[s] the most striking observations and instances from common life; places opposite characters in proper contrast; and alluring us into the paths of virtue by the views of glory and happiness, direct[s] our steps in these paths by the soundest and most illustrious examples. The second, which we might call theoretical philosophy (again, Hume does not give it a name), considers man in the light of a reasonable rather than an active being, and endeavor[s] to form his understanding more than cultivate his manners. In the Enquiry, Hume engages in this second manner of philosophizing. He is aware, he tells us, of extant criticisms of of such activity, especially concerning metaphysics. For he acknowledges that some view metaphysics as painful and fatiguing, the inevitable source of uncertainty and error, arising from the fruitless efforts of vanity and attempting to penetrate into subjects utterly inaccessible to the understanding.

Hume admits that these criticisms might be true; indeed, he seems to think they are true. But it is one thing to level accusations, another to prove them. When Hume encounters these criticisms, he finds that they tend to be based upon mere frustration or revulsion, directed either toward the difficulty of comprehending the metaphysical systems some produce or the apparent absurdity of the results that follow therefrom. He does not, however, find any rational basis for the criticisms, any account that justifies their acceptance. And so he undertakes to enquire seriously into the nature of human understanding, and show, from an exact analysis of its powers and capacity, that it is by no means fitted for such remote and abstruse subjects. His method, he tells us, will be accurate and just reasoning, because it alone [is] able to subvert that abstruse philosophy and metaphysical jargon, which [has] an air of science and wisdom

Now it is not entirely clear which abstruse philosophy and metaphysical jargon is Hume's target. But we can tell a rough (and horribly oversimplified): Descartes initiated a break with medieval philosophy with his Rules for the Direction of the Mind, vowing to reject as false anything that could be doubted and endeavoring to erect, on a sparse but certain foundation, a true system of philosophy (and science). Spinoza, unsatisfied with ambiguities and apparent inconsistencies in Descartes' system, undertook to remove lingering flaws in Descartes' application of his method, purporting to derive from self-evident axioms truths both mundane and profound. Locke, in the meantime, influenced by the success of Newton's philosophical-scientific method, and thereby wary of the possibility of deriving truths about the world from ideas that did not originate in the world, developed an empiricist alternative to the rationalist epistemology found with Descartes and Spinoza, rejecting the existence of innate ideas and purporting to explain all of our ideas as originating, ultimately, in sensory experience. And then Leibniz, dissatisfied with the tensions in Spinoza's philosophy, and unwilling to accept that even our ideas of necessary truths originate in sensory experience, revives rationalism, defending the existence of innate ideas and, with assistance from the Principle of Sufficient Reason, constructing a grand philosophical system able to defuse many popular criticisms of Spinozism. Hume, sharing Locke's empiricist inclinations, thus arrives to find empiricism seemingly refuted by Leibniz's criticisms, replaced by a system purporting to have proved, among other things, that this is the best of all possible worlds, that we have free will despite having no ability to make ourselves act otherwise, that mind and body do not interact, and that, while there are no actual causal relations in the world, there are appearances thereof grounded in a harmony pre-established by an all-perfect, non-deceiving God.

Ideas and Impressions (Enquiry 2)

Following Locke, Hume begins his epistemological investigation by discussing ideas. But, whereas Locke took the only objects of reflection to be ideas, Hume distinguishes between two objects of reflection. The first, following Locke, he calls ideas; the second, inventing his own terminology, he calls impressions. Ideas (or thoughts) are perceptions of copies of our experience, recollections of prior sensations (through memory) or anticipations of future ones (through imagination). Impressions, in contrast, are perceptions the mind has when it is immediately perceiving an object, in the presence of that object. So, for example, the feeling of anger a person has when angry is an impression of anger, and recollection of this impression at a later time is an idea of anger.

Hume never quite offers a definition of idea or impression. Like Locke, he points to examples: when we hear, or see, or feel, or love, or hate, or desire, or will, these activities create impressions in our minds; and when we remember past impressions, our memory creates ideas. Because Hume thinks of a memory as an imperfect reproduction of a prior impression, he characterizes ideas (remembrances of past impressions) as less forcible, vivid, and lively than impressions. (For Hume, ideas are less vivid than impressions in the same way that a copy of a photograph is less vivid than the original photograph. -N.B. This analogy only really makes sense if you think about analog copies.)

Hume is not entirely clear about his reason for making this distinction between ideas and impressions. He presents it as an observation. But it is an observation that seems merely to complicate Locke's theory for no reason, appending things called impressions between sensory experience and simple ideas. This appearance is confirmed, when we find that Hume goes on to endorse Locke's way of ideas, including the distinction between simple and complex ideas and the activity of the mind in constructing complex ideas from simple ones. For example, Hume says that When we think of a golden mountain, we only join two consistent ideas, gold, and mountain, with which we were formerly acquinted.

In fact, Hume follows Locke in taking this way of ideas to support a kind of empiricism (we might call it Humean empiricism) according to which all our ideas are copies of [and so originate with] our impressions. For, he argues, when we analyze our thoughts or ideas, however compounded or sublime, we always find that they resolve themselves into such simple ideas as were copied from a precedent feeling or sentiment [i.e., impression]. Take away the claim that simple ideas originate from memories of impressions, and replace it with the claim that they originate with sensation, and you get Locke's theory. And that theory, recall (from Leibniz), seems to suffer two fatal flaws. First, it cannot explain our perception of the necessity of necessary truths. Second, "there is a great deal innate in our mind, since we are innate to ourselves, so to speak, and since we have within ourselves being, unity, substance, duration, change, action, perception, pleasure, and a thousand other objects of our intellectual ideas; and since "these objects are immediate and always present to our understanding (though they may not always be perceived consciously on account of our distractions and our needs)," our ideas of these objects are innate (Leibniz, Preface to the New Essays).

Hume's distinction between ideas and impressions seems designed to avoid the second of these criticisms. (We have to wait for Hume's response to the first.) For, given this distinction, Hume can maintain that our ideas of being, unity, substance, duration, change, action, perception, pleasure, and so on originate as recollections of impressions. Now even if the ideas originate from impressions, they might still be innate, provided that we have the impressions, and recollections thereof, prior to birth. Here is what Hume has to say about this: If by innate be meant, contemporary to our birth, the dispute

[between rationalists and empiricists] seems to be frivolous; nor is it worth while to enquire at what time thinking begins, whether before, at, or after our birth.

Hume's Fork (Enquiry 4.1)

By the end of 2, Hume takes himself to have motivated the plausibility of the thesis that all ideas are copies of impressions, and he takes this to be the thesis that empiricists like Locke meant to be defend. As to whether or not all impressions originate with sensation, Hume seems not to care. (Indeed, he seems willing to allow that all impressions are innate, for, he wonders, what can be meant by asserting that self-love, or resentment of injuries, or the passion between the sexes is not innate?)

In 4, investigates objects of human reason or enquiry. Hume never explicitly gives a name to these objects. All of the examples he gives are that- clauses: that three times five is equal to half of thirty; that the square of the hypotenuse is equal to the square of the two sides (i.e., Pythagoras's theorem); that the sun will not rise tomorrow. Hume's objects of human reason are what Spinoza called ideas; but we can see, from Hume's examples, that Hume does not use the term idea in the same way that Spinoza does.Nowadays, philosophers call the contents of that- clauses propositions, and I'll follow this convention (even though the terminology is not Hume's he uses objects of human reason).

I don't know why Hume calls these things (propositions) objects of human reason, but here's an idea. Reason is our ability to distinguish the true from the false. (Remember Descartes' natural light of reason?) Ideas (in Hume's sense of the term), while objects of thought, are not objects of reason, because ideas can be neither true nor false. So, for the sake of terminological clarity, and to avoid ambiguity, Hume needs a different term to refer to things that can be true or false. He chooses the phrase objects of reason. I myself prefer proposition, because it is shorter and that's what everyone else calls them nowadays.

Hume makes a distinction (people like to call it Hume's Fork) between two kinds of proposition. He calls the first kind Relations of Ideas, and he gives as examples propositions from geometry, algebra, and arithmetic: that the circumference of a circle equals pi times the square of its radius; that 2x=x2; that 5x3=15. According to Hume, these propositions are discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe.

Hume characterizes Relations of Ideas as intuitively or demonstratively certain, and by this he means that they are true or false of necessity. This distinguishes them from the second kind of proposition, which he calls Matters of Fact, which are not true or false of necessity. For, Hume argues, the contrary of every matter of fact is still possible; because it can never imply a contradiction. This indicates that, according to Hume, the contrary (or denial, or negation) of any true relation of ideas does imply a contradiction. Although Hume is not so explicit, this implication explains why Hume takes Relations of Ideas to be true (or false) of necessity: because they (or their denial) imply a contradiction. And it explains why he thinks we can discover the truth (or falsity) of Relations of Ideas by the mere operation of thought: because deriving contradictions does not require referring to sensation.

Furthermore, although Hume never outright says so, he seems to be committed to the idea that what makes true Relations of Ideas are the definitions or meanings of terms. So, for example, we can derive the truth of 2+2=4 by the mere operation of thought, because we have ideas of what each term in that proposition means, and we can appeal to these meanings to derive a contradiction (such as 0 is not equal to 0) from the negation of that proposition. This approach to Relations of Ideas allows Hume

to rebut Leibniz's other objection to empiricism (namely, its apparent inability to explain how we know the necessity of necessary truths). Consistent with (Humean) empiricism, the ideas that constitute Relations of Ideas are copies of impressions; our knowledge of Relations of Ideas does not depend upon sensory experience; and our knowledge of the necessity of Relations of Ideas is due to the fact that our knowledge of the meanings of their constituent terms allows us to derive contradictions. So, for example, we know that 3x5=15 must be true, because we can appeal to the meanings of 3, x, 5, =, and 15 to derive a contradiction from the proposition that 3x5 does not equal 15.

As for what makes true Matters of Fact, Hume's choice of terminology indicates that he thinks it is the way the world happens to be. Because the world could have been different (this is Leibniz's insight), there is no contradiction in denying any truth that is a Matter of Fact. This raises the question, of course, of how we come to know Matters of Fact. As an empiricist, Hume's answer must be through experience. But Hume undertakes to provide a more detailed answer than this. Before we proceed, however, I want to pause to consider an implication of Hume's Fork for rationalist metaphysic.

The Failure of Rationalism

Hume's Fork entails that all Relations of Ideas (necessary truths) can be known without appeal to experience, that anything that can be known without appeal to experience is a Relation of Ideas, that all Matters of Fact can be known only by appeal to experience, and that anything that can be known only by appeal to experience is a Matter of Fact. These entailments provide Hume with a diagnosis of what went wrong with the grand metaphysical systems of philosophers like Spinoza and Leibniz.

Recall the structure of Spinoza's method. He purports to derive a series of propositions about the world from axioms and definitions. The propositions derived are not Relations of Ideas; for since the world could have been otherwise, they are not necessary truths. So they must be Matters of Fact. The axioms and definitions, however, are supposed to be necessary truths, because they are supposed to be self-evident, such that their denial entails a contradiction. But from necessary truths only necessary truths follow: if the premises of Spinoza's system must be true, the propositions derived therefrom must be true. So Spinoza faces an uncomfortable and unwelcome dilemma: either abandon the claim that the axioms are necessary truths, in which case they are not self-evident and Spinoza's project fails; or else abandon the claim that the derived propositions are about the world, in which case Spinoza system tells us many interesting things about the implications of what we mean by certain words but nothing at all about the way the actual world happens to be. Either way, Spinoza doesn't (and can't) get what he wants. And this is true even if we grant, for the sake of argument, that all of Spinoza's axioms are true and all of his derivations are valid. Similar points hold for Leibniz's method.

Reading AssignmentRequired: Hume, Enquiry 1,2,4.1Optional: Hume Entry in SEP, at .

Discussion Questions1. What is the difference between an impression and an idea? How are they related? How does Hume

use the distinction to reject innate ideas? How might, say, Leibniz respond to Hume's claims?2. What is the difference between Lockean and Humean empiricism? Is Humean empiricism

compatible with, say, Spinozan or Leibnizian rationalism? Does it matter?3. What is Hume's Fork? Is it plausible? What are some implications of Hume's Fork?4. What diagnosis of rationalism does Hume's Form provide? Is this plausible?

Lecture 20 Humean Skepticism

Causation (Enquiry 3-4.1)

Having removed the apparent warrant that necessary truths (Relations of Ideas) provide for the thesis that innate ideas exist, and explained how reason alone suffices as the foundation for knowledge of these truths without dependence on sensation, Hume proceeds to inquire about the foundation for our knowledge of Matters of Fact. His thesis is that all such knowledge is founded on the relation of Cause and Effect.

Hume discusses this cause-and-effect relation in 3. There, he observes that the ideas in our minds are not unconnected from each other, each floating around independent of the others. He thinks, instead, that our minds associate ideas with each other in three basic ways (and, perhaps, combinations of these ways). First, our minds associate ideas via the resembles relation. This association, which Hume calls resemblance, occurs when, for instance, I say Canada and you have an idea of Mexico (the ideas resemble each other by virtue of their objects being neighbors of the United States). Second, our minds associate ideas via the near in time or place relation. Hume calls this contiguity, and it occurs when, for instance, I say beach and you have an idea of the ocean (the ideas are contiguous because their objects are located near each other). Third, our minds associates ideas via the cause-and-effect relation. This occurs when, for instance, when you hear that a loved one has died and then naturally wonder about the cause of death.

Hume argues that, if we want to find warrants for our beliefs concerning Matters of Fact, then, insofar as these beliefs are not merely beliefs about what we are currently experiencing (founded upon sensation) or beliefs about what we have experienced in the past (founded upon memory), we must appeal to this cause-and-effect relation. For it is this relation alone, among the three kinds of relations Hume observes our minds to make, that warrants inferences from facts experienced in the present or the past to facts that have not been experienced. For example, if a man were to find a watch on a deserted island, the foundation for his belief that there is a watch on the island would be his sensory experience of the watch as he sees it before him. But if the man were to come to believe, on the basis of this experience, that there had been men on the island in the past, his sensory experiences provide no foundation for this; he finds no other men on the island, and an absence of sensory evidence is not evidence. If the man infers, from his experience of the watch, but for no reason at all, that there had been other men on the island, his inference would be entirely precarious, which is to say unfounded. But if he were to infer, from his experience of the watch, and for the reason that men cause watches to be present on islands, that there had been other men on the island, his inference would be founded upon this relation of cause-and-effect (and, of course, his sensory experience of the watch).

So Hume's picture is something like this. Sensory experience provides the foundation for beliefs concerning Matters of Fact currently in our presence: if the experience is veridical, these beliefs are true and they are justified by that experience. Memory provides the foundation for beliefs concerning Matters of Fact previously in our experience: if the memory is true, these beliefs are true and they are justified by that memory. All other beliefs concerning Matters of Fact are beliefs about something other than our current or previous experience, and so neither sensory experience nor memory provide a foundation for these beliefs. Instead, for such beliefs, the foundation is a cause-and-effect relation, which either supports an inference from a current or past experience to some effect, or else supports an inference from a current or past experience to some cause. If the cause-and-effect relation is true, the belief for which it is the foundation is true, and that belief is justified by our knowledge of that relation.

Hume proceeds to inquire how we arrive at the knowledge of cause and effect. One answer, and an answer which would be tempting for a rationalist, is that we come to know these relations by deduction (or, as Hume puts it, by reasonings a priori, not dependent on sensory experience). According to this view, we know that fire causes heat because we deduce, for example, from the idea of fire, that fire causes heat. Hume rejects this answer. For, he argues,

Let an object be present to a man of ever so strong natural reason and abilities; if that object be entirely new to him, he will not be able, by the most accurate examination of its sensible qualities, to discover any of its causes or effects.

Hume is asking us to engage in a thought experiment: we are to imagine someone experiencing an object in vivid and excruciating detail, and then decide whether that person would be able to deduce from that experience, without the assistance of other experiences, all the causes and effects of the object. The classic example for this, which Hume discusses later, is the motion of billiard balls: Imagine the cue ball hitting the eight ball, and determine whether, from that experience alone, you can discern whether the cue ball causes the eight ball to move or, instead, that moving magnets underneath the table cause both balls to move in a pre-established manner despite their having the appearance of interaction. Hume takes it to be obvious that deduction would fail to discern causes and effects in his thought experiments. But, in case it is not obvious, he notes that multiple effects are conceivable for any cause, such that not all of them can come to pass; and that multiple causes are conceivable for any effect, such that not all of them are actual causes and such that reason unaided by experience provides no to prefer one possible cause over another. Hume concludes that our reason, unassisted by experience, [can never] draw any inference concerning matter of fact. It follows that causes and effects are discoverable, not by reason, but by experience.

The Problem of Induction (Enquiry 4.2)

If the foundation of (most) of our beliefs about Matters of Fact is the cause-and-effect relation, and the foundation of our beliefs about the cause-and-effect relation is experience, what is the foundation of our beliefs about experience? Hume asks this question in Part 2 of 4, but he investigates a slightly different one. His thesis is that even after we have experience of the operations of cause and effect, our conclusions from that experience are not founded on reasoning, or any process of the understanding. By this, he means to assert that the experiences we have never give us knowledge of cause-and-effect relations.

According to Hume, all of our knowledge concerning cause-and-effect relations comes from experiences, in the past or present, of succession among events. The cue ball moved, and then the eight ball moved. There is no necessary connection between these motions, because the eight ball's motion is not deducible from the idea of the cue ball's motion. There is only an experience of the eight ball moving after the cue ball moves. Now if the cause-and-effect relation is just a relation of constant conjunction, then observing the eight ball moving after the cue ball provides some evidence that the cue ball causes the eight ball to move (because causes must precede their effects). And observing many instances of the eight ball moving after the cue ball moves provides even more evidence for this causal relation. But it does not follow, deductively, from the fact that on many occasions the eight ball moves after the cue ball moves, that on every occasion the eight ball moves after the cue ball moves. So even if the cause-and-effect relation just is the relation of constant conjunction, it seems that experience alone does not provide sufficient evidence for deducing knowledge of constant conjunctions between events.

Hume allows that this demand, that experience provide a deductive foundation for knowledge of causal relations, is perhaps asking too much of experience. For, one might suppose, experience provides an inductive foundation for such knowledge. For if we add to experience the principle that if something has always been observed to be followed by such-and-such an event, then it always is followed by that event, then we can deduce knowledge of constant conjunctions between events from past experiences of conjunctions between those events and this principle.

This principle, that future events will resemble past events, is the foundation for what we nowadays call inductive generalization. This is a form of reasoning in which one infers that something true of a sample is true of a population that contains that sample. Hume thinks that this principle is the foundation of our beliefs concerning cause-and-effect relations: all arguments from experience are founded on the similarity, which we discover among natural objects, and by which we are induced to expect effects similar to those, which we have found to follow from such objects; from causes, which appear similar, we expect similar effects. Following convention, let's call this the principle of induction.

So far, then, Hume has it that: (most) of our beliefs concerning Matters of Fact are founded upon relations of cause and effect; and our beliefs concerning relations of cause and effect are founded upon the principle of induction. Because we know something only if we know its foundation, it follows that we have knowledge concerning (most) Matters of Fact only if we have knowledge of causal relations, and that we have knowledge of causal relations only if we have knowledge of the principle of induction. The problem of induction is the problem of finding a foundation for our knowledge of the principle of induction. Hume thinks the problem is insoluble, and his reason for thinking this is known as Hume's Dilemma.

Hume's Dilemma is (in logician's terminology) a destructive dilemma: Either we know the principle of induction deductively (through reason), or we know the principle of induction inductively (through experience). But we cannot know the principle deductively, because no contradiction follows from supposing that the principle is false. (In Leibniz's terminology, the principle is not absolutely necessary.) Nor can we know the principle inductively. For It is impossible that any arguments from experience can prove this resemblance of the past to the future; since all these arguments are founded on the supposition of that resemblance. That is, even if the principle is born out in all past experiences, we would need to appeal to the principle itself in order to infer that the principle is true of all possible experiences; but appealing to the principle in order to justify the principle is engaging in circular reasoning, and circular reasoning does not provide knowledge. So we cannot know the principle of induction.

Humean Projectivism (Enquiry 5)

Hume's Dilemma entails that we cannot know the principle of induction. It follows that we cannot have knowledge of causal relations, and further that most of our beliefs concerning Matters of Fact do not qualify as knowledge. This is Humean Skepticism. But Hume is not content to establish the truth of a certain kind of skepticism. For he observes that

in all reasonings from experience, there is a step taken by the mind, which is not supported by any argument or process of the understanding; [but] there is no danger that these reasonings, on which almost all knowledge depends, will ever be affected by such a discovery. If the mind be

not engaged by argument to make this step, it must be induced by some other principle; and that principle will preserve its influence as long as human nature remains the same.

The idea underlying this observation is that even if we cannot know many things concerning Matters of Fact, perhaps we can translate the content of what we can't know into a content that we can know, and perhaps figuring out why we make (unjustified) inductive inferences will help us to figure our how this translation should go.

Hume's observation is that, even though inductive reasoning does not provide knowledge, we can't stop ourselves from reasoning inductively. If we did, we would never form beliefs about anything beyond our immediate or past experiences. But if it just not feasible, for beings like us, to restrict ourselves to this meager set of beliefs. (For one thing, we'd probably die quickly.)

Hume hypothesizes that the cause of our inductive inferences is custom or habit rather than reason. For wherever the repetition of any particular act or operation produces a propensity to renew the same act or operation, without being impelled by any reasoning or process of the understanding; we always say, that this propensity is the effect of Custom. Custom, for Hume, is our propensity to act in a certain way, based upon our actions, and the actions of others, in the past. (Example: Americans drive on the right side of the road because of custom; Brits drive on the left side of the road because of custom; and reason does not determine that one custom, rather than the other, is the true or proper one.) And his hypothesis is that we reason in accordance with the principle of induction, not because there is a good reason to do so, but rather because that is our custom. Whence he says that All belief of matter of fact is derived merely from some object, present to the memory or senses, and a customary conjunction between that and some other object. Or in other words; having found, in many instances, that two kind of object have always been conjoined together, the mind is carried by custom to infer that they are always conjoined together. (And since, for Hume, causation is constant conjunction, this means that the mind is carried by custom to infer that there is a relation of cause-and-effect between the objects.)

This view, that our mind imposes cause-and-effect relations onto ideas from our experience, is a form of what philosophers nowadays call projectivism. Projectivism is the view that some of our beliefs about the world are projections of our minds. And in Hume's case, this is the thesis that our minds gild and stain the world with causal relations. This does not mean, of course, that the projections we make are false. But, in the absence of a refutation of Hume's Dilemma, it means, for the case of causation, that the projections, even if true, cannot be known to be true.

The appeal to custom allows Hume to provide a skeptical solution to the problem of induction. For even though we cannot know propositions concerning the causal connections between events in the world, we can know propositions concerning the connections our mind makes between ideas of events in the world. For Hume holds that the custom of making inductive inferences is an operation of the soul that is unavoidable, a species of natural instinct. So we can know that our minds make associations of cause-and-effect relations by observing our minds in action. This means that, while we cannot know that the cue ball caused the eight ball to move, we can know that our mind associated the cue ball with the eight ball via the relation of cause-and-effect. If we recast all propositions about causation as propositions about our reactions to sensations and memories, our ability to know that our mind imposes causal associations onto the world means that we can know some propositions that do not concern the content of our immediate or past experiences, namely, those propositions that concern the way in which our mind associates ideas about objects of our immediate or past experiences.

Reading AssignmentRequired: Hume, Enquiry 3-5Optional: Beisecker on Hume, at .

Discussion Questions1. According to Hume, what are the foundations for our beliefs concerning Matters of Fact? Is this view

plausible?2. Why, according to Hume, does reason fail to provide us with knowledge of cause-and-effect

relations? Is his argument persuasive?3. What is the problem of induction? What would a solution to the problem of induction look like?4. What is Hume's Dilemma? What does it show? How does it show this? Is there a way to avoid it?5. What is Hume's solution to the problem of induction? Is it satisfying?