Hume Against Descartes

8/12/2019 Hume Against Descartes

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Hume against Descartes

"Des Cartesmaintained that thought was the essence of the mind; not this thought or that

thought, but thought in general. This seems to be absolutely unintelligible, since every thing, that

exists, is particular: And therefore it must be our several particular perceptions, that compose themind. I say, composethe mind, not belongto it. The mind is not a substance, in which the

perceptions inhere... We have no idea of substance of any kind, since we have no idea but what is

derived from some impression, and we have no impression of any substance either material or

spiritual. We know nothing but particular qualities and perceptions." - David Hume,Abstract of

A Treatise of Human Nature

How does Hume come to this critique of Descartes? InAn Enquiry concerning Human

UnderstandingHume lays out the grounds of his epistemology.

First, we must divide the perceptions of the mind into impressions and ideas. Impressions are

vivid and immediate perceptions, such as warmth or the agitations we feel from love. Ideas are

less vivid and mediated by memory (in recollection) or imagination (in anticipation). They are

further distinguished by their source and associated liberties; impressions flow from the body

which is confined "to one planet," while ideas flow from the mind and admit of unbounded

manipulation (with the exception of whatever implies an absolute contradiction).

Upon careful consideration, it occurs to us that all ideas are either compounded of simpler ideas

or otherwise simple and identifiable as a copy of an impression. [There is an "insignificant"

counter example concerning the simple idea of a particular color or note that is derived not fromimpressions, but from its difference from other things of the same kind.] So we can safely banish

all assent to any idea that cannot be traced to an impression. It can be said at this point that

because we have no impression of substance itself we have no clear and distinct idea of the mind

as a substance, so 'I' cannot be said to be a substance which essentially thinks.

But perhaps the mind is essentially the source of the particular principles of the understanding?

Now it is clear that one idea leads to another, and so there is some principle of the association of

ideas. When we reflect upon these associations, we find three principles governing them:

resemblance, contiguity, and causality. Perhaps causal relations are known not by experience but

rather by reason a priori. However, reason cannot give us certainty of an effect from a particular

cause, as we only get the idea of causality from our experience of constant conjunction that we

habitually assume will continue in an orderly manner. Thus it is only by experience and habit

that we believe the future will resemble the past, and that the principles of the association of

ideas will continue to be as they have been. So the immutability of the mind (needed for claims

about the essence of the mind) cannot be known, and we are not entitled to say that the mind is


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essentially the source of the principles of the understanding. At most we can say that nature has

given us a marvelous instinct by which we understand the world, yet nothing can give us

certainty that nature and instinct will always exhibit the order we now perceive in them.

Thomas Reid (and David Hume) on Induction, CausalityIntroduction

Philosopher Thomas Reid's significance in regard to induction does not derive from his own inductive theory,

as in Aristotle's case or Francis Bacon's. In fact, he explicitly states that he has adopted Bacon's method of

induction in hisInquiry into the Human Mind, and gives Lord Bacon nothing but the highest praise. What

makes Reid so significant is that he understood Hume's criticism of causality (in An Enquiry Concerning

Human Understanding), interpreted what it would imply about induction and inductive reasoning, and offereda sort of counterargument to Hume's skeptical doubts.

[I'll abbreviate Hume'sAn Enquiry Concerning Human Understandingas simplyAn Enquiry, and

Reid'sInquiry into the Human MindasInquiry, since I cite those works so much.]

Before we can understand Reid's points about induction, then, we must first understand Hume.

Hume's Inductive Practice: A Brief Aside

David Hume has been seen as the great skeptic of induction, but he didn't think of himself that way. He uses

induction on numerous points in his philosophy, including his views on causality, as we will see. He quotes

approvingly of some lines of thought in Bacon's method of induction in the section on "miracles" inhisEnquiryon the understanding, and utilizes Bacon's notion of a "crucial experiment" (a technical term in

Baconian induction) to make a point of his own in section 5 of his An Enquiry into the Sources of Morals.

But Hume certainly was a skeptic of causality; or at the very least, the human capacity to truly discover and

understand it. Causality has an intimate relationship to induction, and Bacon, Hume, and Reid all recognize it,

each in their own ways. For some reason, Hume thought it necessary to question our knowledge of causality

without considering it's impact on the validity of inductive reasoning. And even in this skepticism of causes, he

isn't consistent: he names four mechanistic causes as ones that we did in fact discover (elasticity, gravity,

cohesive of objects, and moving other objects through mechanical force). In any event, Hume does say things

about causality, to which we'll now turn.

Hume on Causality and Human Knowledge

Sensible Qualities, Secret Powers

Let's consider some examples to clarify Hume's positions, examples that Hume and Reid use. A man eats a

piece of bread and is thereby nourished; a child touches a flame and experiences pain; a person touches the

point of a pin and pricks himself. In cases like these, Hume distinguishes between the sensible qualities of

objects that we're aware of in experience, and the secret powers of things that enable things do or carry out

certain actions: "The bread that I formerly ate nourished me; i.e. a body with such and such sensible qualities


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did at that time have such and such secret powers." (An Enquiry, Sect 4, Part 2) A flame with such and such

sensible qualities (light, warmth) causes a child pain when he tries to handle it, and thus has some kind of

secret power.

Hume denies that there's a valid way to sense or reason from the experience of objects' sensible qualities to

their secret powers or how those secretive qualities were produced, whether by experience or by rational

demonstration:

The qualities of an object that appear to the senses never reveal the causes that produced the object or the

effects that it will have; nor can our reason, unaided by experience, ever draw any conclusion about real

existence and matters of fact. (An Enquiry, Section 4, Part 1)

Our senses tell us about the colour, weight and consistency [that is, cohesion; not just a pile of grains] of bread;

but neither the senses nor reason can ever tell us about the qualities that enable bread to nourish a human

body. (An Enquiry, Sect 4, Part 2)

To know about matters of fact, we have to know the relation between cause and effect, and to know about this,

we have to consult experience, Hume believes. But all experience seems to show us is (1) the sensible qualities

of things and (2) that some secret powers are being made manifest, such as fire burning something else. When

asked the question "What are inferences from experience based on?" Hume concludes that reason and thesenses must be silent. He goes on to say:

Despite this ignorance of natural powers and forces, however, we always assume that the same sensible

qualities will have the same secret powers, and we expect them to have the same effects that we have found

them to have in our past experience. (ibid., part 2)

Hume provides the explanation for this soon afterward, in a chain of reasoning central to his criticism of

causality and our ability to know it.

The Future Will (Not) Resemble the Past

Hume remarks that all inferences from experience are founded upon the similarities found among things in

nature (for instance, several different fires), from which we expect that the effects of these similar things will

also be similar. In other words, our inferences from experience really come from this principle: "From causes

that appear similar we expect similar effects." (ibid.) After experiencing similar events a number of times, we

infer a connection between the sensible qualities and the secret powers, but for Hume this is no different than

saying from perceiving what we take to be a cause, we mentally connect it to what we take to be the effect.

Thus Hume discovers the basis for inferences from experience: we assume that the future will resemble the

past, and that similar powers will be combined with similar sensible qualities (ibid.). If, however, we presume

that the courses of nature may not stay the same, then the past can no longer assist in our knowing about the

future, and experience is rendered useless for subsequent inferences. Hume has no problem making this

presumption:

However regular the course of things has been, that fact on its own doesnt prove that the future will also beregular. Its no use your claiming to have learned the nature of bodies from your past experience. Their secret

nature, and consequently all their effects and influence, may change without any change in their sensible

qualities. (ibid.)

Loaves of bread, for instance, may have nourished me in the past, but the sensible qualities of tomorrow's loaf

won't reveal that it has already been poisoned and thus possesses different, destructive secret powers.

Hume began this inquiry into causality with a question revolving around the nature of knowledge concerning


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matters of fact; to answer this, he would need to know the foundation of the relation between cause and effect;

and to answer that, he would need to know what accounts for our inferences from experience. Throughout the

inquiry, Hume has denied that the senses or the faculty of reason can account for matters of fact, real and

genuine causes and effects, or the principle that the future will resemble the past. What Hume does think

accounts for all of these is "custom," or human habit or instinct.

[Custom] alone is what makes our experience useful to us, and makes us expect future sequences of events to belike ones that have appeared in the past. Without the influence of custom, we would be entirely ignorant of

every matter of fact beyond what is immediately present to the memory and senses. (ibid.)

All beliefs about matters of fact or real existence are derived merely from something that is present to the

memory or senses, and a customary association of that with some other thing. (ibid.)

So for Hume, our "matters of fact" are really just events, some composed of the sensible qualities we experience,

others involving the secret powers latent in objects of nature. When we regularly experience a certain kind of

sensible quality (or set of qualities) and observe that it's followed by a certain kind of secret powerwhen we

observe nature's regularitywe come to infer or believe that there's a connection between the two, so that one

becomes the cause, the other the effect. This inference or association is something built into the human

constitution, a human custom or habit that we can't help engaging in. In this way, we come to believe that the

future will resemble the past, and we believe that with the appearance of a cause we should expect an effect.

Reid on Causality

The Inductive Principle

Reid's critical comments on causality and induction appear in his work Inquiry into the Human Mind, in the

final section on his chapter about "Seeing." After discussing the forces or powers by which we receive

information from others through language, he explains how we gain information about nature, in a set of

passages strikingly similar to Hume's.

In human experience, we constantly find things conjoined in the course of nature, and after a number of

occasions of similar things, we come to observe the appearance of one as a sign that the other will immediatelyfollow it and we believe that it follows. In other words, the "regularity of nature" or the constancy of nature's

laws in the past somehow lead to us to mentally connect what we take to be the cause (or sign) with what we

take to be the effect (or thing signified). It is this aspect of our mind's constitution from which we

unquestionably assent that the future will resemble the past, or a sort of "...foreknowledge that things you have

found conjoined in the past will be conjoined in the future." (Inquiry, Ch. 6 Sec. 24)

Thisaspect is what Reid calls the "inductive principle": it is the natural force by which we rely on the

continuance of nature's laws, without which our "experience" would be useless or even detrimental to our lives.

This, Reid observes, is a self-evident truthan axiomof our knowledge of nature, including inductive

thinking. Like Hume, he initially wonders about how we reached this conviction about nature's regularity.

What makes [the inductive principle] evident to us?[...] True; experience informs us that [natural events] have

been conjoined in the past; but no-one has ever had any experience of what is future, and that's our question

How do we come to believe that the future will be like the past? (ibid.)

Reid denies that sense-perception reveals this, as we "...don't perceive in any natural cause any real causality or

effectiveness, but only a connection established in the course of nature between [the natural cause] and what is

called its 'effect'." (ibid.) Likewise, he denies that reason has any role in making these kind of connections or

convictions, and ascribes its origin to instinct:


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...[Reason] can't have given rise to this belief [in the first place], for children and idiots [that is, mentally

handicapped] have this belief as soon as they know that fire will burn them. So it must be an effect of instinct,

not of reason. (ibid.)

[...]

However, I agree with Hume that our belief in the continuance of natures law is not derived from reason. It is

an instinctive foreknowledge of the operations of nature, very like the foreknowledge of human actions that

makes us rely on the testimony of our fellow creatures; and just as we need the latter if we are to be able toreceive information from men by language, so we need the former if we are to be able to receive information

about nature by means of experience. (ibid.)

The "inductive principle" is something built into the human mind, and according to Reid, it is the basis for all

acquired perceptions, for all inductive reasoning, and for all reasoning from analogy. We suddenly have a smell

sensation, and later associate it with baked chicken, and due to the inductive principle, we continue to believe

that we're perceiving a baked piece of chicken whenever we have a similar smell sensation in the futurethis is

acquired perception. We play in a body of water and nearly drown, and thanks to the inductive principle, we

learn to be more cautious around bodies of water when we encounter them later on; and from this, we come to

reason generally that "water can make us drown"--this is inductive reasoning.

Both acquired perception and inductive reasoning rely on the inductive principle, and this instinctual principle

(and the surrounding context from which it arises) seems to differ very little from Hume's account of our

thinking of cause-and-effect, and its basis in habit or custom. This raises a number of questions:

Why does Reid think induction is valid, if inductive reasoning isn't even how we reach causal connections?

Why does he say, "[...]let sound induction alone govern our belief" in chapter 3 of his work,Essays on the

Intellectual Powers of Man?

Why does he accept Bacon's method of induction as a great example of inductive theory, and Newton's work

on gravitation and optics as great examples of inductive practice?

What gives?

The Interpretation of Signs

All our knowledge of nature beyond our original perceptions is acquired by experience, and consists in the

interpretation of signs. (Inquiry, Ch. 6, Sec. 24) Up until now, Reids writing on this interpretation of signs

has focused on an instinctual relating of causes with their effects, differing from Humes reasoning concerning

our knowledge of causality in only minor details. The key difference lies in how long Reid and Hume think we

are governed by this inductive principle, this habitual or instinctual reliance on the continued regularity of

nature.

Lets think of Hume and Reids inductive principle as a kind of mechanical unionjust as there's a regularity

of nature, of events that we term "causes" and "effects," there is a corresponding regularity in our conception of

these things or events, such that the occurrence of one is followed by the belief in the existence of the other.

Take a child reciting the number line, for instance: you might ask him to count one to ten, and for him that's

what "number line" means, such that if he's prompted to give the number line again, he'll simply count one toten. He doesn't yet know what those numbers are, but he's associated it with the phrase "number line," as a

mechanical unionfor him, the existence of one implies the existence of the other.

Hume thinks that this mechanical union is simply how we understand cause-and-effect and matters of fact

there's no escape from it. "These operations of the soul are a kind of natural instinct, which no reasoning or

process of the thought and understanding can either produce or prevent." (An Enquiry, Sec. 5, Part 1) But Reid

disagrees, and says that, "[this inductive] force, like the force for trust [in people's words], is unlimited in

infancy and is gradually restrained and regulated as we grow up." (Inquiry, Ch. 6, Sec. 24) What replaces it,


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eventually, is reason. Eventually, we learn to stop believing anything that comes out of people's mouthswe

learn not to automatically trust themand we start to reason and examine or analyze what people say.

Similarly, we eventually learn not to place our faith in any and all natural events, and gain the ability to reason

about the origin and processes of natural events.

Human reason is not infallible: just as we misinterpret what people say sometimes, we can misinterpret what

natural events tell us. The comparison between people's words and natural events ends here, however, sinceReid believes that nature cannot deceive us, whereas people can lie. Hume believed that reason never touched

or governed our beliefs in causes and effects, or generally in matters of fact; Reid implies that it can, if we use

our reason to interpret nature.

In effect, this is Reid's counter-argument to Hume: (1) though it is true that we all experience the "inductive

principle" or various mechanical unions, it is eventually restrained by our reason, and (2) we can use our reason

to learn about true causes and effects, and actual matters of fact.

With that said, how do we learn about these true causes and sound interpretations of nature, in Reid's view?

Induction, and the Language of Nature

The language of nature is what we all study, and the students of it belong to different classes.[...] Philosophers

[which includes "scientists" in Reid's time] fill up the top class in this school, and are scholars of the language of

nature. (ibid.)

Natural events can be likened to nature's documents, composed of signs, and it is our responsibility as students

of nature to learn how to soundly and legitimately interpret them. Animals, children, the mentally challenged,

ordinary men, and philosophers/scientists comprise different classes, but experience is our only teacher.

Though experience is enlightened by the inductive principle, this alone does not result in sound interpretations

of nature: we require tutors. The tutoring and education provided by nature is enough to sustain a savage's

manner of life, if he takes the appropriate actions; the tutoring offered by human education, in addition to that

of nature, "can make a good citizen, a skillful artisan, or a well bred man." (ibid.) To be able to soundly interpret

nature with reasoning, we need not only natural and human education, but the kind of tutoring that could form

a "Rousseau, a Bacon, or a Newton," the kind that only reason and reflection can instill. (ibid.)

Reid calls Bacon's work, theNovum Organum(New Instrument), a "grammar of the language of nature,"

something which displays the rules of inductive reasoning, including the idols or fallacious concepts that cause

us to often misinterpret nature. (ibid.) And he considers Newton'sPrincipia Mathemtica(specifically Book 3)

and Opticsas the best models of inductive reasoning. Bacon formulated the method by which we could properly

think inductively, and avoid misinterpreting nature; Newton explained how experimental philosophy could find

true causes (and thus make accurate theories), and provided the world with two mechanical theories as

evidence, namely his theories on universal gravitation and optics. He says that Newton learned his method of

natural philosophy from Bacon's rules of induction, and states something important about induction:

The purpose of all those rules is to teach us to distinguish seeming or apparent connections of things in the

course of nature from ones that are real. (ibid.)

For Reid, Bacon and Newton were the valedictorians or magna cum laude of the school of nature, and it is their

contributions to human reasoningwhat they've said about causality, experimental philosophy, and

inductionthat is at the heart of his confidence in induction. The accomplishments of these two philosophers

are the reasons why he thinks we can truly understand natural facts and causality.

Hume Against Descartes

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