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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that nothing is known. The thesis was inspired by Socrates’ avowal that the

only thing he knew was that he knew nothing. Thus, it asserts that knowledge

is impossible. This form of Scepticism seems to be susceptible to an objection

raised by the Stoic Antipater (fl. c. 135 BCE) and others that the view is self-

contradictory. To know that knowledge is impossible is to know something;

hence, dogmatic Scepticism is false.

Carneades (c. 213-129 BCE), a member of the Academy, gave a subtle

reply. Academic Scepticism, he claimed, should not be interpreted as a claim

about how the world is in itself or about a correspondence between thought

(or language) and the world, but as a judicial decision. Just as a defendant in a

trial does not prove his innocence but relies upon its presumption and defends

it against attack, so the sceptic does not try to prove that he knows nothing but

presumes it and defends this presumption against attacks.

Carneades’ construal of Academic Scepticism brings it close to the other

kind, Pyrrhonism, named after Pyrrho of Elis (c. 365-275 BCE). None of his

works survive, and scholars rely principally on the early 3rd-century-CE

writings of Sextus Empiricus to understand Pyrrhonism. Pyrrhonists assert or

deny nothing but lead people to give up making any claims to knowledge. The

Pyrrhonist’s strategy is to show that, for each proposition with some evidence

for it, an opposed proposition has equally good evidence supporting it. These

arguments for refuting each side of an issue are called “tropes.” For example,

the judgment that a tower is round when seen at a distance is contradicted by

the judgment that the tower is square when seen up close. The judgment that

Providence cares for all things, based upon the orderliness of the heavenly

bodies, is opposed by the judgment that many good people suffer misery and

many bad people enjoy happiness. The judgment that apples have many

properties – shape, color, taste, and aroma – each of which affects a sense

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organ, is opposed by the equally good possibility that apples have only one

property that affects each sense organ differently.

Pyrrhonists diagnose dogmatism as the unjustifiable preference for one

mode of existence over another. Dogmatists prefer wakefulness and sanity

over sleep and insanity. But why should sleep and insanity not be the norm? If

the dogmatist answers that it is because sleep and insanity involve some

deficiency or abnormal physical states, the sceptic replies, “By what

nonquestion-begging criterion are these things said to be deficient or

abnormal? Why should insanity not be taken as the primary notion and sanity

be defined as the lack of insanity? If it were, then it would not be difficult to

see sanity as a deficiency or abnormality, just as insanity currently is. Or why

should wakefulness not be seen as the deficient condition in which people do

not dream?” The sceptic does not advocate insanity or sleep but merely argues

that a preference for them is no less justified than a preference for sanity and

wakefulness.

What is at stake in the preceding sceptical arguments is “the problem of

the criterion,” that is, the problem of deciding how one can determine a

justifiable standard against which to measure judgments. Truth seems to need

a criterion. But every criterion is either groundless or inconclusive. Suppose

that something is proffered as a criterion. The sceptic will ask what proof

there is for it. If no proof is offered, the criterion is groundless. If, on the other

hand, a proof is produced, a vicious circle begins to close around the

dogmatist: What judgment justifies belief in the proof? If there is no

judgment, the proof is unsupported; and if there is a judgment, it requires a

criterion, which is just what the dogmatist was supposed to have provided in

the first place.

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If the sceptic needed to make judgments in order to survive, he would be

in trouble. In fact there is another method of survival that bypasses judgment.

The sceptic can live quite nicely, according to Sextus, by following custom

and the way things appear to him. In doing this, the sceptic does not judge the

correctness of anything but merely accepts appearances for what they are.

Ancient Pyrrhonism is not strictly an epistemology since it has no theory

of knowledge and is content to undermine the dogmatic epistemologies of

others, especially of the Stoics and Epicureans. Pyrrho himself was said to

have had moral and ethical motives for attacking dogmatists. Being reconciled

to not knowing anything, Pyrrho thought, induced serenity (ataraxia).

St. Augustine

St. Augustine of Hippo (354-430) claimed that human knowledge would

be impossible if God did not illumine the human mind and thereby allow it to

see, grasp, or understand ideas. There are two components to his theory: ideas

and illumination. Ideas as Augustine construed them are the same as Plato’s;

they are timeless, immutable, and accessible only to the mind, not to the

senses. They are indeed in some mysterious way part of God and seen in God.

Illumination, the other element of the theory, was for Augustine and his many

followers, at least through the 14th century, a technical term, built upon a

metaphor. Since the mind is immaterial, it cannot be literally lighted. Yet the

entire theory of illumination rested upon the extended visual metaphor,

inherited from Plotinus (205-270) and other Neoplatonic sources, of the

human mind as an eye that can see when and only when God, the source of

light, illumines it. Still, it is a powerful metaphor relied upon even in the 17th

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century by René Descartes (Discourse on Method; 1637). Varying his

metaphor, Augustine sometimes says that the human mind participates in God

and even, as in On the Teacher, that Christ illumines the mind by dwelling in

it. It is important to emphasize that Augustine’s theory of illumination

concerns all knowledge, and not specifically mystical or spiritual knowledge.

In addition to its historical significance, his theory is interesting for showing

how diverse epistemological theories have been.

Before he articulated this theory in his mature years and soon after his

conversion to Christianity, Augustine was concerned to refute the Scepticism

of the Academy. In Against the Academicians Augustine claims that, if

nothing else, humans know such disjunctive tautologies as that either there is

one world or there is not one world and that either the world is finite or it is

infinite. Humans also know many propositions that begin with the phrase “It

appears to me that,” such as “It appears to me that what I perceive is made up

of earth and sky, or what appears to be earth and sky.” And they know logical

(or what he calls “dialectical”) propositions, for example, “If there are four

elements in the world, there are not five; if there is one sun, there are not two;

one and the same soul cannot die and still be immortal; and man cannot at the

same time be happy and unhappy.”

Many other refutations of Scepticism occur in later works, notably, in

On the Free Choice of the Will, On the Trinity, and The City of God. In the

latter work Augustine proposes other examples of things about which people

are absolutely certain. Again in explicit refutation of the Sceptics of the

Academy, Augustine argues that if a person is deceived, then it is certain that

he exists. Like Descartes, Augustine puts the point in the first person, “If I am

deceived, then I exist” (Si fallor, sum). A variation on this line of reasoning

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occurs in On the Trinity, when he says that if he is deceived, he is at least

certain that he is alive.

Augustine also points out that, since he knows, he knows that he knows;

and he notes that this can be reiterated an infinite number of times: If I know

that I know that I am alive, then I know that I know that I know that I am

alive. This point was codified in 20th-century epistemic logic as the axiom “If

X knows that p, then X knows that X knows that p.” In The City of God

Augustine claims that he knows that he loves: “For neither am I deceived in

this, that I love, since in those things which I love I am not deceived.” With

Scepticism thus refuted, Augustine simply denies that he has ever been able to

doubt what he had learned through his sensations or even the testimony of

most people.

Scepticism did not recover from Augustine’s criticisms for a thousand

years; but then it arose again like the phoenix in Egyptian mythology.

Augustine’s Platonic epistemology dominated the Middle Ages until the mid-

13th century, when St. Albertus Magnus (1200-80) and then his student St.

Thomas Aquinas developed an alternative to Augustinian illuminationism.

Medieval Philosophy

St. Anselm of Canterbury

The phrase St. Anselm of Canterbury (c. 1033-1109) used to describe his

own project, namely, “faith seeking reason” (fides quaerens intellectum), well

characterizes medieval philosophy as a whole. All the great medieval

philosophers, Christian, Jewish, and Islamic alike, were also theologians.

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Virtually every object of interest was related to their belief in God, and

virtually every solution to every problem, including the problem of

knowledge, contained God as an essential part. Anselm himself said that,

while true propositions are those that signify what is, ultimately truth is God.

This presented Anselm with a problem, which he discusses at the beginning of

Proslogium as a prelude to his famous ontological argument for the existence

of God. There is a tension between the view that God is truth and

intelligibility and the fact that humans have no perception of God. How can

there be knowledge of God, he asks, when all knowledge comes through the

senses and God, being immaterial, cannot be sensed? His solution is to

distinguish between knowing something by being acquainted with it in

sensation and knowing something by describing it. Knowledge by description

is possible because of the concepts that one forms from sensation. All

knowledge about God depends upon the description that he is “the thing than

which a greater cannot be conceived.” From this premise Anselm argues that

humans can know, for example, that God exists, is all-powerful, all-knowing,

all-just, all-merciful, and immaterial. Eight hundred years later Bertrand

Russell would use the same distinction between knowledge by acquaintance

and knowledge by description to develop his influential philosophy, although

he would have vigorously denied that the distinction could be employed as

Anselm had, namely, to prove that God exists.

St. Thomas Aquinas

While a Platonic and Augustinian epistemology dominated the early

Middle Ages, the translation of Aristotle’s On the Soul in the early 13th

century had a dramatic effect. Following Aristotle, Thomas Aquinas (1225-

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74) recognized that there are different kinds of knowledge. Sense knowledge

is what results from sensing individual things: thus, one sees a tree, hears the

song of an oriole, and tastes or smells a peach. Thomas considered sense

knowledge to be low-grade because it has individual things as its object and is

also shared with brute animals. Sensation itself does not involve the intellect

and is not properly speaking knowledge (scientia).

It is characteristic of scientific knowledge to be universal; the more

general in scope a piece of knowledge is, the better. This is not to diminish the

importance of specificity. Scientific knowledge should also be rich in detail,

and God’s knowledge is the most detailed. The detail, however, must be

essential to the thing being studied and not peculiar to just some instances of

that kind. Although Thomas thought that the highest knowledge humans can

possess is knowledge of God, knowledge of physical objects is more attuned

to human capabilities, and only that kind of knowledge will be discussed here.

In his discussion of knowledge in Summa theologiae, Thomas Aquinas

argues that human beings do not know material objects directly, nor are such

things the principal object of knowledge. Knowledge aims at what is

universal, while material things are individual and can be known only

indirectly. Elaborating on the thought of Aristotle, Thomas claims that the

process of thinking that accompanies knowledge consists of the active

intellect (intellectus agens) abstracting (abstrahens) a concept from an image

(phantasma) received from the senses.

In one of Thomas’ accounts of the process, abstraction is the process of

isolating the universal elements of an image of a particular object from those

elements that are peculiar to the object. For example, from the image of a dog

the intellect abstracts the ideas of being alive, being capable of reproduction,

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movement, and whatever else might be essential to being a dog. All these

ideas are common to all dogs because they are essential to them. These ideas

can be contrasted with the ideas of being owned by Dion and weighing five

pounds, namely, with properties that vary from dog to dog.

As stated earlier, Aristotle typically spoke of a form as being in the

intellect of the knower, whereas the matter of an object is unintelligible and

remains extramental. While it was necessary for Aristotle to say something

like this in order to escape the absurdity of holding that a material object is in

the mind in exactly the same way it is in the physical world, there is also

something unsatisfying about it. Physical things contain matter as an essential

element, and, if their matter is no part of what is known, then it seems that

human knowledge is lacking. In order to counter this worry, Thomas revised

Aristotle’s theory. He said that not the form alone but the species of an object

is also in the intellect. A species is a combination of form and “common

matter” (materia communis), where common matter is contrasted with

individuated matter (materia signata vel individualis), which actually gives

bulk to a material object. Common matter is something like a general idea of

matter. Since every animal must have a body, it is not enough to conceive of

an animal merely as something that is alive. Having flesh and bones, that is,

being material, is part of the essence of being an animal. Of course this

materiality, which is common to every animal, is not the same as the actual

flesh and bone that constitute Fido – hence the distinction between common

and individuated matter.

This abstracted species resides in a part of the soul called “the passive

intellect,” where it is described as being illumined by the active intellect.

What this process amounts to is the isolation of those features of the

intelligible species that are universal and necessary to it. Thus, to know what a

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human being is is to have abstracted the ideas of being rational and being

capable of sensation, movement, reproduction, and nutrition and to have

excluded the ideas of living in a particular place or having a certain

appearance, all of which are not essential to being human.

One objection that Thomas anticipated being raised against his theory is

that it gives the impression that ideas, not things, are what are known. If

knowledge is something that humans have and if what humans have in their

intellect is a species of a thing, then it is the species that is known and not the

thing. It might seem, then, that Thomas’ view is a type of idealism.

Thomas had prepared for this kind of objection in several ways. His

insistence that what the knower has in his intellect is a species, which includes

matter, is supposed to make what is in the intellect seem more like the object

of knowledge than an immaterial Aristotelian form. Also, scientific

knowledge does not aim at knowing any individual object but at what is

common to all things of a certain sort. In this, Thomas’ views are similar to

those of 20th-century science. The billiard ball that John Jones drops from his

porch is of no direct concern to physics. Even though its laws apply to John

Jones’s ball, physics is interested in what happens to any object dropped from

any height, just as what Thomas says about apples in general also applies to

each individual apple.

As assuaging as these considerations might be, they do not blunt the

main force of the objection. For this purpose Thomas Aquinas introduced the

distinction between what is known and that by which it is known. To specify

what is known, say, an individual dog, is to specify the object of knowledge;

to specify that by which it is known, say, the phantasm or the species of a dog,

is to specify the apparatus of knowledge. The species of something is that by

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which the thing is known; but it is not itself the object of that knowledge,

although it can become an object of knowledge by being reflected upon.

The philosophical optimism of the 13th century dissolved as a

consequence of the secular and ecclesiastical condemnations in 1270 and 1277

of certain aspects of Aristotelian philosophy, and worries about sceptical

consequences began to emerge. While the philosophy of Thomas Aquinas was

one of the targets of these condemnations, John Duns Scotus was also worried

about the sceptical consequences that could be elicited from the major

competitor to Aristotelianism, the Augustinianism of Henry of Ghent (1217-

93). According to Henry, God must “illumine” the human intellect on every

occasion of its knowing. Not only could no good literal meaning be given to

this sense of illumination, but the view also sounds as if all human knowledge

were supernatural. Henry’s insistence that God’s illumination is a natural

divine illumination did not persuade many people.

John Duns Scotus

While he accepted some aspects of Aristotelian abstractionism and also

held that there need to be some a priori principles of perception, principles

that he attributed to Augustine, John Duns Scotus (c. 1266-1308) did not rest

the certainty of human knowledge on either of them. He distinguished four

different classes of things that are certain: First, there are things that are

knowable simply (simpliciter). These include both true identity statements

such as “Cicero is Tully” and propositions, later to be called analytic, such as

“Man is rational.” According to Duns Scotus, such truths coincide with what

makes them true. A consequence of this is that the negation of a simple truth