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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to a claim. If A states that he has had a certain experience, for instance, that of

having personally spoken with Smith, who assured him he would keep his

appointment at 9:00 AM, then the skeptic can point out that, although one

could have such an experience, it is still possible that Smith might not show

up; and, if so, A’s claim to know is untenable. In effect, by emphasizing the

notion of possibility, the skeptic is pointing out that there is a logical gap

between the criteria that support the claim and the claim itself. The criteria

might be satisfied, and yet the claim might be false; but, if such a possibility

exists, the original assertion cannot be a specimen of knowing.

More generally, radical scepticism has tried to show that one might (i.e.,

could possibly) have all the experiences associated with normal perception or

behavior and yet be wholly mistaken in thinking that these experiences

correlate with anything in the external world. For example, a brain in a vat

might be programmed by scientists to have the sensation of seeing a tree, even

though it is not in fact seeing a tree. Thus, there is a gap between the

experience the brain is having and external reality; accordingly, its claim to

know on the basis of such a visual experience is mistaken. The skeptic’s point

is that the disparity between external reality and felt experience is always

possible and, accordingly, that knowledge claims based upon such experience

cannot be defended.

The ability to find counterexamples explains why Sceptics do not

challenge but indeed accept the dogmatist’s definition of knowledge. That

they do so is important because it means that they are not arguing at cross-

purposes with their opponents. What they challenge is not the meaning of

knowledge but the contention that anybody actually has knowledge in that

sense.

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Nearly all of the major epistemological theories of philosophy have

given rise to sceptical reactions. Many of the greatest thinkers in the Western

tradition have assumed that by means of reason or sense experience one can

come to have knowledge of reality. But scepticism has challenged the validity

of both of these appeals. Sceptics have developed wholesale arguments to

undermine the efforts to show that reason and sense experience, which seem

to be the only possible candidates, are reliable sources of knowledge.

Descartes, for example, considered the hypothesis that an evil genius may

delude people into thinking that they are experiencing the real world when

they are not. With regard to major epistemological problems, such as the

“other-minds problem,” the problem of memory, the problem of induction,

and the problem of self-knowledge, sceptical doubts have challenged the

validity of reason and of sense experience and thus of claims to have

knowledge of various aspects of reality. How some of these moves and

countermoves actually take place are addressed below.

The History of Epistemology

Ancient Philosophy

Pre-Socratics

The central focus of ancient Greek philosophy was its attempt to solve

the problem of motion. Many pre-Socratic philosophers thought that no

logically coherent account of motion and change could be given. This problem

was a concern of metaphysics, not epistemology, however, and in the present

context it suffices merely to allude to the arguments of Parmenides and Zeno

of Elea against the possibility that anything moves or changes. The

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consequence of this position for epistemology was that all major Greek

philosophers held that knowledge must not itself change or be changeable in

any respect. This requirement motivated Parmenides, for example, to hold that

thinking is identical with being (what exists or is unchanging) and that it is

impossible to think of “nonbeing” or “becoming” (what changes) in any way.

Plato

Plato (c. 427-347 BCE) accepted the Parmenidean constraint on any

theory of knowledge that both knowledge and its objects must be unchanging.

One consequence of this, as Plato pointed out in Theaetetus, is that knowledge

cannot have physical reality as its object. In particular, since sensation and

perception have various kinds of motions as their objects, knowledge cannot

be the same as sensation or perception. The negative thesis of Plato’s

epistemology consists, then, in the denial that sense experience can be a

source of knowledge on the ground that the objects apprehended through the

senses are subject to change. To the extent that humans have knowledge, they

attain it by transcending the information provided by the senses in order to

discover unchanging objects. But this can be done only by the exercise of

reason, and in particular by the application of the dialectical method of inquiry

inherited from Socrates.

The Platonic theory of knowledge is thus divided into two parts: a quest

first to discover whether there are any unchanging objects and to identify and

describe them and second to illustrate how they could be known by the use of

reason, that is, via the dialectical method. Plato used various literary devices

for illustrating his theory; the most famous of these is the allegory of the cave

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in Book VII of The Republic. The allegory depicts ordinary people as living

locked in a cave, which represents the world of sense-experience; in the cave

people see only unreal objects, shadows, or images. But through a painful

process, which involves the rejection and overcoming of the familiar sensible

world, they begin an ascent out of the cave into reality; this process is the

analogue of the application of the dialectical method, which allows one to

apprehend unchanging objects and thus acquire knowledge. In the allegory,

this upward process, which not everyone is competent to engage in,

culminates in the direct vision of the sun, which represents the source of

knowledge.

In searching for unchanging objects, Plato begins his quest by pointing

out that every faculty in the human mind apprehends a set of unique objects:

hearing apprehends sounds but not odours; the sense of smell apprehends

odours but not visual images; and so forth. Knowing is also a mental faculty,

and therefore there must be objects that it apprehends. These have to be

unchanging, whatever they are. Plato’s discovery is that there are such

entities. Roughly, they are the items denoted by predicate terms in language:

such words as “good,” “white,” or “triangle.” To say “This is a triangle” is to

attribute a certain property, that of being a triangle, to a certain spatiotemporal

object, such as a particular figure drawn on a blackboard. Plato is here

distinguishing between specific triangles that can be drawn, sketched, or

painted and the common property they share, that of being triangular. Objects

of the former kind he calls particulars. They are always located somewhere in

the space-time order, that is, in the world of appearance. But such particular

things are different from the common property they share. That is, if x is a

triangle, and y is a triangle, and z is a triangle, x, y, and z are particulars that

share a common property, triangularity. That common property is what Plato

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calls a “form” or “idea” (not using this latter term in any psychological sense).

Unlike particulars, forms do not exist in the space-time order. Moreover, they

do not change. They are thus the objects that one must apprehend in order to

acquire knowledge.

Similar remarks apply, for example, to goodness, whiteness, or being to

the right of. Particular things change; they come into and go out of existence.

But whiteness never changes, and neither does triangularity; and, if they do

not change, they are not subject to the ravages of time. In that sense, they are

eternal.

The use of reason for discovering unchanging forms is exercised in the

dialectical method. The method is one of question and answer, designed to

elicit a real definition. By a “real definition” is meant a set of necessary and

sufficient conditions that exactly delimit a concept. One may, for example,

consider the concept of being the brother of Y. This can be explained in terms

of the concepts of being male and of being a sibling of Y. These concepts

together lay down necessary and sufficient conditions for anything’s being a

brother. One who grasps these conditions understands precisely what it is to

be a brother.

The Republic begins with the use of the dialectical method to discover

what justice is. Cephalus proposes the thesis that “justice” means the same as

“honesty in word and deed.” Socrates searches for and finds a counterexample

to this proposal. It is just, he points out, under some conditions, not to tell the

truth or to repay debts. If one had borrowed a weapon from an insane person,

who then demanded it back in order to kill an innocent person, it would be just

to lie to him, stating that one no longer had the weapon. Therefore, “justice”

cannot mean the same as “honesty in word” (i.e., telling the truth). By this

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technique of proposing one definition after another and subjecting each to

possible counterexamples, Socrates attempts to find a definition that would be

immune to counterexamples. To find such a definition would be to define the

concept of justice, and in this way to discover the true nature of justice. In

such a case one would be apprehending a form, the common feature that all

just things share.

Plato’s search for definitions and thereby the nature of forms is a search

for knowledge. But how should knowledge in general be defined? In

Theaetetus Plato argues that it involves true belief. No one can know what is

false. A person may mistakenly believe that he knows something, which is in

fact false, but this is only thinking that one knows, not knowing. Thus, a

person may confidently assert, “I know that Columbus was the first European

to land in North America” and be unaware that other Europeans, including

Erik the Red, preceded Columbus. So knowledge is at least true belief, but it

must also be something more. Suppose that someone believes there will be an

earthquake in September because of a dream he had in April and that there in

fact is an earthquake in September, although there is no connection between

the dream and the earthquake. That person has a true belief about the

earthquake but not knowledge. What the person lacks is a good reason

supporting his true belief. In a word, the person lacks justification for it. Thus,

in Theaetetus, Plato concludes that knowledge is justified true belief.

Although it is difficult to explain what justification is, most philosophers

accepted the Platonic analysis of knowledge as fundamentally correct until

1963, when the American philosopher Edmund L. Gettier produced a

counterexample that shook the foundations of epistemology: suppose that

Kathy knows Oscar very well and that Oscar is behind her, out of sight,

walking across the mall. Further, suppose that in front of her she sees walking

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toward her someone who looks exactly like Oscar; unbeknownst to her, it is

Oscar’s twin brother. Kathy forms the belief that Oscar is walking across the

mall. Her belief is true, because he is walking across the mall (though she

does not see him doing it). And her true belief seems to be justified, because

she formed it on the same basis she would have if she had actually seen Oscar

walking across the mall. Nonetheless, Kathy does not know that Oscar is

walking across the mall, because the justification for her true belief is not the

right kind. What her true belief lacks is an appropriate causal connection to its

object.

Aristotle

In Posterior Analytics, Aristotle (384-22 BCE) analyzes scientific

knowledge in terms of necessary propositions that express causal relations.

Such knowledge takes the form of categorical syllogisms, in which the middle

term causally and necessarily connects the major and minor terms. For

example, because all stars are distant and all distant objects twinkle, it follows

that all stars twinkle. That is, the middle term, “distant objects,” connects the

minor term, “stars,” to the major term, “twinkle,” in order to yield the

conclusion that all stars twinkle. Aristotle, however, recognizes that not all

knowledge is provable. Thus, the premises of the most basic syllogisms are

known but not provable. In contrast with scientific knowledge, there is

opinion, which is not provable and is about what happens to be true but need

not be.

Since the knowledge formulated in syllogisms resides in the mind,

which is part of or one faculty of the soul, much of what Aristotle says about

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knowledge is part of his doctrine about the nature of soul and, in particular,

human soul. As he uses the term, every living thing, including plant life, has a

soul (psyche), a soul being what makes a thing alive. Thus it is important not

to equate soul with mind or intellect. The intellect (nous) might variously be

described as a power, faculty, part, or aspect of the human soul. It should be

stressed that for Aristotle the terms soul (psyche) and intellect (nous) and its

constituents were understood to be scientific terms.

Knowledge is something that a person has. Thus it must be in him

somewhere, and the location must be his mind or intellect. Yet there can be no

knowledge if the knower and the thing known are wholly separate. What then

is the relation between the knowledge in the person or his mind and the object

of his knowledge? Aristotle’s answer is one of his most enigmatic claims. He

says, “Actual knowledge is identical with its object.”

Here is one suggestion about what Aristotle means. When a person

learns something, he acquires something. What he acquires must either be

something different from the thing he knows or identical with it. If it is

something different, then there is a discrepancy between what he has in mind

and the intended object of his knowledge. But such a discrepancy seems to be

incompatible with the existence of knowledge. For knowledge, which must be

true and accurate, cannot deviate from its object in any way. One cannot know

that blue is a color if the object of that knowledge is something other than that

blue is a color. This idea that knowledge is identical with its object is dimly

reflected in the repetition of the variable p in the standard formula about

knowledge: S knows that p just in case it is true that p. Although the line of

thinking being attributed to Aristotle is defective in several ways, something

like it seems to have motivated Aristotle and many other thinkers over the

centuries.

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To assert that knowledge and its object must be identical raises a

question: In what way is knowledge in a person? Suppose that Smith knows

Fido. Then Fido is in Smith. Obviously, Fido is not there as he exists in the

nonmental world of space and time. In what sense can it be true that a person

who knows what a dog is has that object in his mind? Aristotle derives his

answer from his general theory of reality. According to him, all (terrestrial)

substances are composed of two principles: matter and form. If there are four

dogs – Bowser, Fido, Spot, and Spuds – they are the same in some respect and

different in some respect. They are the same in that each belongs to the same

kind and each function similarly. Thus, Aristotle reasons, just as Plato had,

that there must be something in virtue of which they are the same, and this he

calls “form.” That is, Bowser, Fido, Spot, and Spuds each have the very same

form of being a dog. They are different in that they are made out of different

matter, different parcels of stuff. The form that a thing has is more important

than its matter because it is the form that makes the thing what it is. If Fido

were to lose the form of being a dog and acquire another, he would no longer

be the same thing. The stuff out of which Fido is made is not similarly

important, and in fact that stuff changes periodically, as body cells change

through metabolic processes, without Fido ceasing to be Fido.

To return to the explanation of knowledge, what is in the knower when

he knows what dogs are is the form of being a dog minus the matter.

According to Aristotle, matter is literally unintelligible and not essential to

what Fido or any other dog is; thus its absence is inconsequential for

knowledge, though not for Fido.

In his sketchy account of the process of thinking in De anima (On the

Soul), Aristotle says that the intellect, like everything else, must have two

parts: something analogous to matter and something analogous to form. The

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first of these is the passive intellect; the second is active intellect, of which

Aristotle speaks tersely. “Intellect in this sense is separable, impassible,

unmixed, since it is in its essential nature activity.... When intellect is set free

from its present conditions it appears as just what it is and nothing more: it

alone is immortal and eternal... and without it nothing thinks.”

This part of Aristotle’s views about knowledge is an extension of what

he says about sensation. According to Aristotle, sensation occurs when the

sense organ is stimulated by the sense object, typically through some medium,

such as light for vision and air for hearing. This stimulation causes a “sensible

species” to be generated in the sense organ itself. This “species” is some sort

of representation of the object sensed. As Aristotle describes the process, the

sense receives “the form of sensible objects without the matter, just as the wax

receives the impression of the signet-ring without the iron or the gold.” But,

since there are different species for each of the five external senses that

Aristotle recognized – sight, hearing, touch, taste, and smell – ”species” does

not mean “image.”

Ancient Scepticism

After the development of Aristotle’s psychology the next significant

event for the theory of knowledge was the rise of Scepticism, of which there

were at least two kinds. The first, Academic Scepticism, arose in the Academy

after Plato’s death and was propounded by the Greek philosopher Arcesilaus

(c. 315-c. 240 BCE), about whom the philosophers Cicero, Sextus Empiricus,

and Diogenes Laërtius provide information. Academic Scepticism is also

called “dogmatic Scepticism” when it is interpreted as arguing for the thesis