Ridling Zaine. Philosophy: Then and Now. A look back at 26 centuries of thought

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Ridling, Philosophy Then and Now: A Look Back at 26 Centuries of Thought

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Because of their correspondence, there seems to be a special connection

between simple impressions and simple ideas: the former cause the latter.

Hume deduces this on the following grounds. A simple impression always

precedes the corresponding idea, and the idea invariably follows the conjoined

impression. Thus, because of the temporal priority of impressions and the

constant conjunction of impressions and ideas, Hume concludes that

impressions cause ideas.

There are two kinds of impressions: sensation and reflection. Sensation

“arises in the soul originally from unknown causes.” Hume says little more

about sensation because discussion of it belongs to anatomists and scientists.

(Many late 20th-century philosophers do not accept this division between

philosophy and anatomy.) To explain reflection is rather complicated because

it derives from a complex mental operation. After people feel heat or cold,

thirst or hunger, pleasure or pain, they form ideas of heat or cold, thirst or

hunger, pleasure or pain. And, following the formation of these ideas – at a

third stage of cogitation – they form from the ideas the second kind of

impressions: impressions of “desire and aversion, hope and fear.” These

impressions are the result of reflecting on ideas caused by sensation.

Since imagination can divide and assemble disparate ideas as it will,

some explanation is needed for why the mind seems to run in predictable

channels. Hume says that the mind is guided by three principles: resemblance,

contiguity, and cause and effect. Thus a person who thinks of one idea is

likely to think of another idea that resembles it. For example, a person’s

thought, if one accepts Hume’s account, will run from red to pink to white, or

from dog to wolf to coyote. Hume also uses the principle of resemblance to

explain how general ideas function. Hume agrees with Berkeley in denying

that there are abstract ideas, and he affirms that all ideas are particular. Some

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of them, however, are used to represent many objects by inclining the mind to

think of other ideas that resemble the first. These particular ideas that

represent many things are general ideas. Concerning contiguity, people are

inclined to think of things that are next to each other in space and time. Finally

and most importantly, people associate ideas on the basis of cause and effect

relations. Fire and smoke, parent and child, disease and death are tied in the

mind because of their causal relations. But cause and effect relations play a

more central role in Hume’s thought than these brief remarks might suggest.

Cause and Effect

Although people gain much information from their impressions, most

matters of fact depend upon reasoning about causes and effects, even though

people do not directly experience causal relations. What, then, are causal

relations? According to Hume they have three components: contiguity of time

and place, temporal priority of the cause, and constant conjunction. In order

for x to be the cause of y, x and y must exist adjacent to each other in space

and time, x must precede y, and x and y must invariably exist together. There

is nothing more to the idea of causality than this; in particular, people do not

experience and do not know of any power, energy, or secret force that causes

possess and that they transfer to the effect. Still, all judgments about causes

and their effects are based upon experience. To cite examples from An

Enquiry Concerning Human Understanding (1748), since there is nothing in

the experience of seeing a fire close by which logically requires that one will

feel heat, and since there is nothing in the experience of seeing one rolling

billiard ball contact another that logically requires the second one to begin

moving, why does one expect heat to be felt and the second ball to roll? The

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explanation is custom. In previous experiences, the feeling of heat has

regularly accompanied the sight of fire, and the motion of one billiard ball has

accompanied the motion of another. Thus the mind becomes accustomed to

certain expectations. “All inferences from experience, therefore, are effects of

custom, not of reasoning.” Thus it is that custom, not reason, is the great guide

of life. In short, the idea of cause and effect is neither a relation of ideas nor a

matter of fact. Although it is not a perception and not rationally justified, it is

crucial to human survival and a central aspect of human cognition.

Substance

One of the cornerstones of philosophy from Plato to Berkeley was the

notion of substance, that which exists in itself and does not depend upon

anything else for its existence. Substance is contrasted with accident or modes

of being, which exist in substances and depend on them for their existence. A

dog is a substance, and its color, shape, weight, and bark exist in the dog and

depend on it for their existence. One of the reasons for Hume’s place in the

history of philosophy is that he denied the existence of substance, using the

epistemological principles he shared, not simply with empiricists like Locke

and Berkeley, but with Aristotle and Aquinas as well. As argued in the

Treatise, since all human knowledge must be traced back to sensation, the

idea of substance must be also. But what sensation can give rise to the idea of

substance? It is not a color, shape, sound, or taste. Substance, by its

proponents’ own definition, is not an accident or mode. Hume concludes, “We

have therefore no idea of substance, distinct from that of a collection of

particular qualities, nor have we any other meaning when we either talk or

reason concerning it.” What then are the things that earlier philosophers

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designated substances? They are “nothing but a collection of simple ideas, that

are united by the imagination, and have a particular name assigned to them.”

Gold, to take Hume’s example, is nothing but the collection of the ideas of

yellow, malleable, fusible, and so on. Even the mind is only a collection, “a

heap or collection of different perceptions united together by certain relations

and suppos’d tho’ falsely, to be endow’d with a perfect simplicity or identity.”

Relations of Ideas and Matters of Fact

Human thought concerns two kinds of things: relations of ideas and

matters of fact. Relations of ideas can either be intuited, that is, seen directly,

or deduced from other propositions. That a is identical with a, that b

resembles c, and that d is larger than e are examples of propositions that are

intuited. The opposites of true propositions expressing relations of ideas are

contradictory. Arithmetic and algebra are the subjects about which there can

be the most certainty. In his Treatise Hume says that geometry is almost as

certain as these, but not quite, because its original principles derive from

sensation, and about sensation there can never be absolute certainty. He

revised his views about geometry later, and in the Enquiry he puts geometry

on an equal footing with the other mathematical sciences.

In contrast with relations of ideas, matters of fact are derived from

experience. Experience, however, would be quite limited if it did not include

causal relations, which go beyond what is experienced.

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Scepticism

Hume’s discussion about relations of ideas and matters of fact gives the

impression that he thought that human knowledge is possible. Relations of

ideas seem to be the object of knowledge, while matters of fact seem to be the

object of probability. In Part II of the Treatise he denies this and argues

forcefully for Scepticism.

Until the beginning of Part IV of Book I of the Treatise, there is little or

no hint of Scepticism. The distinction between knowledge (of the

mathematical sciences) and probability (of matters of fact) seems to

presuppose that there is knowledge. But one then discovers that Scepticism

undermines it all. Although the rules of science are certain and infallible, the

application of those rules by humans is uncertain and fallible because humans

are prone to error. It does no good for a person to try to check his chain of

reasonings because the process of checking is no more immune to error than

the original calculation. How can one know that the checking process was

performed correctly? And, if the checking procedure seems to identify a

mistake in the original calculation, how can one determine whether the error is

in the original or in the seeming identification of an error? Adding a checking

procedure is in one respect worse than leaving the original calculation alone.

It introduces a second event, which, like the original calculation, is possibly

flawed. And it is more probable that one of two possibly flawed events is

flawed than either one of the two alone. “By this means,” Hume says, “all

knowledge degenerates into probability.” Another way to see this

consequence is to consider that reason is a cause of truth. But, since all causal

relations are probable, not certain, all human reasoning is at best probable.

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If one thinks further about the matter, the probability of knowledge

diminishes and doubt increases. Each judgment of the probability of some

judgment introduces further reasons for doubt and thus lowers the overall

probability. The joint probability of p and q is lower than the probability of p;

and the joint probability of p, q, and r is lower than the probability of p and q.

Ultimately, “when I proceed still farther, to turn the scrutiny against every

successive estimation I make of my faculties all the rules of logic require a

diminution, and at last a total extinction of belief and evidence.” If one should

say, “Surely, you are kidding,” Hume’s answer would be a beguiling one: In a

sense, “yes,” for nature has so made human beings that they cannot in fact be

sceptical even though the argument for Scepticism is cogent. As Hume says in

his Enquiry, people conduct their lives for the most part governed by custom

and nature, not reason. Scepticism is true even though there are no Sceptics,

because, as in Berkeley’s philosophy, the arguments for Scepticism “admit of

no answer and produce no conviction.”

There is another way of expressing Hume’s position. If one examines

the grounds that human beings have for trusting their reasoning, one will not

be able to find rational grounds. Reason cannot be rationally grounded, and

the ground of rationality is wholly nonrational: “belief is more properly an act

of the sensitive, than of the cogitative part of our natures.”

Some people have tried to make short shrift of Scepticism by pointing

out that if the sceptic recognizes his arguments to be rationally compelling,

then he must recognize the sovereignty of reason and hence the falsity of

Scepticism. Hume points out that the battle against Scepticism cannot be won

in this way. Scepticism is a refutation of the claims of reason. As such, one

assumes the truth of rationalism in order to show that it is contradictory and

hence false. In other words, Hume’s proof is a reductio ad absurdum

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argument against belief in rationality. The sceptical argument proceeds by

arguing that, if rationalism is true, then it is not rational to be rational. Since

the consequent is contradictory, the assumption that rationalism is true must

be false. Thus, rationalism is false.

Hume has been called “the complete Pyrrhonist,” but Hume himself

denied that he was one, in large part because he did not distinguish between

Pyrrhonism and Academic Scepticism, both of which, according to him,

advocate the suspension of belief even as one conducts one’s ordinary affairs.

Hume thought such a program impossible for human beings: humans are

condemned to believe. Unlike the Pyrrhonist, Hume does not suspend

judgment or abandon reason. He judges according to reason because it is his

nature to do so even though sceptical arguments against reason are cogent.

This philosophical schizophrenia – the use and trust in reason coupled with

the recognition that rationality has no rational justification – is part of what

Hume calls “mitigated Scepticism.” Another part of it is restricting one’s

investigations to topics that are within the “narrow capacity of human

understanding,” namely to experience and the mathematical sciences.

Given his Scepticism, one might wonder whether it could be directed

against Hume’s own positive doctrine. It can. At the end of Part I of his

Treatise Hume says, “Can I be sure, that in leaving all establish’d opinions I

am following truth; and by what criterion shall I distinguish her, even if

fortune shou’d at last guide me on her foot-steps? After the most accurate and

exact of my reasonings, I can give no reason why I shou’d assent to it; and

feel nothing but a strong propensity to consider objects strongly in that view,

under which they appear to me.” Ultimately one judges according to custom

and the way nature dictates one must judge. The Enquiry Concerning Human

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Understanding is intended to be an accurate description of how people judge,

not a justification of it.

Immanuel Kant

Idealism is often defined as the view that everything which exists is

mental; that is, everything is either a mind or depends for its existence upon a

mind, as do ideas and thinking. Immanuel Kant (1724-1804) was not strictly

an idealist according to this definition, although he called himself a

“transcendental idealist.” On his view, humans can know only what is

presented to their senses or what is contributed by their own mind. Every

sensory experience is a mixture of a sensory content, which is simply given to

a person, and a spatial and temporal form, which is contributed by the mind

itself. Further, if one formulates a sensory experience into a judgment, then

the mind also contributes certain additional objective features: the judgment

incorporates ideas of something being a substance or quality of that substance,

ideas of one thing causing another, or one thing being related by necessity or

by accident to another. In short, the raw data of sensory input is only a small

part of what constitutes human knowledge. Most of it is contributed by the

human mind itself; and, so far as human knowledge is concerned, rather than

the mind trying to accommodate itself to the external world, the world

conforms to the requirements of human sensibility and rationality. Kant

compared his radical reorientation of the way philosophers ought to study

human knowledge to the Copernican revolution in astronomy. Just as the

Earth revolves around the Sun, contrary to common sense, objects conform

themselves to the human mind, contrary to common sense.

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Kant’s idealism notwithstanding, he also believed that a world existed

independent of the human mind and completely unknowable by it. This world

consists of things-in-themselves, which do not exist in space and time, are not

organized in causal relations, and so on, because these are elements

contributed by the human mind as conditions for knowing. Because of his

commitment to realism (minimal though it may be) Kant was disturbed by

Berkeley’s uncompromising idealism, which amounted to a denial of the

external world. Kant found this incredible and rejected “the absurd conclusion

that there can be appearance without anything that appears.”

Kant’s goal, as developed in Critique of Pure Reason (1781), was to

supplant Berkeley’s crude idealism with a transcendental idealism. The

difference, as Kant saw it, is that, while Berkeley began empirically by noting

that everything that humans are rationally justified in asserting to exist is

related to consciousness, he went on to ask what necessary conditions underlie

any empirical experience at all. Kant did not deny that there is empirical

experience, but he was critical of Berkeley for not excavating its rational

underpinnings. Kant is called a “rationalist” because he thought that the

conditions for empirical experience can only be reasoned to, not discovered

in, experience; he called his idealism “transcendental” because the conditions

he was looking for are common to – they transcend – any experience. In his

notorious “proof of an external world,” he claimed that he experienced

himself as an object in time, that time requires something permanent outside

of his consciousness as a precondition for his existence in time, and hence that

an external world exists. In other words, the claim is that inner experience

presupposes an outer or external world. But few philosophers have claimed to

understand why this should be so, and the very contrast of inner and outer

seems to beg the question.

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Kant believed that all objects of sensation must be experienced within

the limits of space or time. Thus, all physical objects have a spatiotemporal

location. Because space and time are the backdrop for all sensations, he called

them pure forms of sensibility. In addition to these forms, there are also pure

forms of understanding, that is, categories or general structures of thought that

the human mind contributes in order to understand physical phenomena. Thus,

every empirical object is thought to have some cause, to be either a substance

or part of some substance, and so on. The structure of judgments finally leads

to the question of what properties the propositions that express judgments (or

knowledge) have.

From a logical point of view, the propositions that express human

knowledge can be divided according to two distinctions. First is the distinction

between propositions that are a priori, in the sense that they are knowable

prior to experience, and those that are a posteriori, in the sense that they are

knowable only after experience. Second is the distinction between

propositions that are analytic, that is, those in which the predicate is included

in the subject, and those that are synthetic, that is, those in which the predicate

is not included in the subject. Putting the terms of these two distinctions

together yields a fourfold classification of propositions. (1) Analytic a priori

propositions include “All bachelors are unmarried” and “All squares have four

sides.” (2) Analytic a posteriori propositions do not exist, according to Kant,

because, if the predicate is conceptually included in the subject, the appeal to

experience is irrelevant and unnecessary. Also, the negation of an analytic

proposition is a contradiction; but, because any experience is contingent, its

opposite is logically possible and hence not contradictory. (3) Synthetic a

priori propositions include “Every event has a cause” and “7 + 5 = 12.”

Although it is not part of the concept of an event that it be a cause, it is