Principles like those Parmenides assumed are said in contemporary jargon to be a priori principles, or principles of reason, which just means that they are known prior to experience. It is not that we learn these principles first chronologically but rather that our knowledge of them does not depend on our senses. For example, consider the principle “You can’t make something out of nothing. ” If you wished to defend this principle, would you proceed by conducting an experiment in which you tried to make something out of nothing?
In fact, you would not. You would base your defense on our inability to conceive of ever making something out of nothing Everything we know originates from four sources. The first, our senses, can be thought of as our primary source of information. Two other sources, reason and intuition, are derivative in the sense that they produce new facts from data already supplied to our minds. The fourth source, authority (or “hearsay,” or “testimony” of others), is by nature secondary, and secondhand fact-claims are always more wiggly and difficult to validate.
Other sources of knowledge are commonly claimed, and it is not inconceivable that there might exist other sources; but if they do exist, knowledge derived from them is problematic, and careful analysis usually finds that they can be subsumed under one or more of the four known sources and must be seriously questioned as legitimate, separate sources of reliable information. In summary, what is the nature of our knowledge about the real world of objects/events?
Our knowledge of reality is composed of ideas our minds have created on the basis of our sensory experience. It is a fabric of knowledge woven by the mind. Knowledge is not given to the mind; nothing is “poured” into it. Rather, the mind manufactures perceptions, concepts, ideas, beliefs, and so forth and holds them as working hypotheses about external reality. Every idea is a (subjective) working model that enables us to handle real objects/events with some degree of pragmatic efficiency.
However persuasive our thoughts and images may be, they are only remote representations of reality; they are tools that enable us to deal with reality. It is as though we draw nondimensional maps to help us understand four-dimensional territory. The semanticists have long reminded us to beware of confusing any sort of map with the real landscape. “The map,” they say, “is not the territory. ”
An abstraction, by definition, is an idea created by the mind to refer to all objects which, possessing certain characteristics in common, are thought of in the same class. The number of objects in the class can range from two to infinity. We can refer to all men, all hurricanes, all books, all energy-forms—all everything. While abstraction-building is an inescapable mental process—in fact it is the first step in the organization of our knowledge of objects/events—a serious problem is inherent in the process.
At high levels of abstraction we tend to group together objects that have but a few qualities in common, and our abstractions may be almost meaningless, without our knowing it. We fall into the habit of using familiar abstractions and fail to realize how empty they are. For example, what do the objects in the following abstractions have in common? All atheists, all Western imperialists, all blacks or all whites (and if you think it’s skin color, think twice), all conservatives, all trees, all French people, all Christians.
When we think in such high-level abstractions, it is often the case that we are communicating nothing meaningful at all. “The individual object or event we are naming, of course, has no name and belongs to no class until we put it in one. ” Going as far back as Plato, philosophers have traditionally defined knowledge as true justified belief.
A priori knowledge is knowledge that is justified independently of (or prior to) experience. What kinds of knowledge could be justified without any appeal to experience? Certainly, we can know the truth of definitions and logical truths apart from experience. Hence, definitions and logically necessary truths are examples of a priori knowledge. For example, “All unicorns are one-horned creatures” is true by definition.
Similarly, the following statement is a sure bet: “Either my university’s football team will win their next game or they won’t. ” Even if they tie or the game is canceled, this would fulfill the “they won’t win” part of the prediction. Hence, this statement expresses a logically necessary truth about the football team. These two statements are cases of a priori knowledge. Notice that in the particular examples of a priori knowledge I have chosen, they do not give us any real, factual information about the world. Even though the statement about unicorns is true, it does not tell us whether there are any unicorns in the world.
Similarly, the football prediction does not tell us the actual outcome of the game. Experience of the world is required to know these things. The second kind of knowledge is a posteriori knowledge, or knowledge that is based on (or posterior to) experience. Similarly, the adjective empirical refers to anything that is based on experience. Any claims based on experience purport to add new information to the subject. Hence, “Water freezes at 32 degrees Fahrenheit” and “Tadpoles become frogs” would be examples of a posteriori knowledge. We know the freezing point of water and the life cycle of tadpoles through experience.
Thus far, most philosophers would agree on these points. The difficult question now arises: Is there any a priori knowledge that does give us knowledge about the real world? What would that be like? It would be knowledge expressible in a statement such that (a) its truth is not determined solely by the meaning of its terms and (b) it does provide information about the way the world is. Furthermore, since it is a priori, it would be knowledge that we could justify through reason, independently of experience. The question, then, is whether or not reason alone can tell us about the ultimate nature of reality. 1.
Is it possible to have knowledge at all? 2. Does reason provide us with knowledge of the world independently of experience? 3. Does our knowledge represent reality as it really is? Rationalism claims that reason or the intellect is the primary source of our fundamental knowledge about reality. Nonrationalists agree that we can use reason to draw conclusions from the information provided by sense experience. However, what distinguishes the rationalists is that they claim that reason can give us knowledge apart from experience.
For example, the rationalists point out that we can arrive at mathematical truths about circles or triangles without having to measure, experiment with, or experience circular or triangular objects. We do so by constructing rational, deductive proofs that lead to absolutely indubitable conclusions that are always universally true of the world outside our minds (a priori knowledge about the world).
Obviously, the rationalists think the second question should be answered affirmatively. Empiricism is the claim that sense experience is the sole source of our knowledge about the world. Empiricists insist that when we start life, the original equipment of our intellect is a tabula rasa, or blank tablet.
Only through experience does that empty mind become filled with content. Various empiricists give different explanations of the nature of logical and mathematical truths. They are all agreed, however, that these truths are not already latent in the mind before we discover them and that there is no genuine a priori knowledge about the nature of reality. The empiricists would respond “No! ” to the second epistemological question. With respect to question 3, both the rationalists and the empiricists think that our knowledge does represent reality as it really is.
Constructivism is used in this discussion to refer to the claim that knowledge is neither already in the mind nor passively received from experience, but that the mind constructs knowledge out of the materials of experience. Immanuel Kant, an 18th-century German philosopher, introduced this view. He was influenced by both the rationalists and the empiricists and attempted to reach a compromise between them. While Kant did not agree with the rationalists on everything, he did believe we can have a priori knowledge of the world as we experience it.
Although Kant did not use this label, I call his position constructivism to capture his distinctive account of knowledge. One troubling consequence of his view was that because the mind imposes its own order on experience, we can never know reality as it is in itself. We can only know reality as it appears to us after it has been filtered and processed by our minds.
Hence, Kant answers question 3 negatively. Nevertheless, because Kant thought our minds all have the same cognitive structure, he thought we are able to arrive at universal and objective knowledge within the boundaries of the human situation. Before reading further, look at the highway picture for an example of a classic experiment in perception.
Did you get the right answer, or were your eyes fooled? One way that skeptics attack knowledge claims is to point to all the ways in which we have been deceived by illusions. Our experience with perceptual illusions shows that in the past we have been mistaken about what we thought we knew. These mistakes lead, the skeptic claims, to the conclusion that we can never be certain about our beliefs, from which it follows that our beliefs are not justified. Another, similar strategy of the skeptic is to point to the possibility that our apprehension of reality could be systematically flawed in some way.
The story of Ludwig, the brain in the vat who experienced a false virtual reality, would be an example of this strategy. Another strategy is to suppose that there is an inherent flaw in human psychology such that our beliefs never correspond to reality. I call these possible scenarios universal belief falsifiers. The characteristics of a universal belief falsifier are (1) it is a theoretically possible state of affairs, (2) we have no way of knowing if this state of affairs is actual or not, and (3) if this state of affairs is actual, we would never be able to distinguish beliefs that are true from beliefs that seem to be true but are actually false. Note that the skeptic does not need to prove that these possibilities are actual.
For example, the skeptic does not have to establish that we really are brains in a vat, but merely that this condition is possible. Furthermore, the skeptic need not claim that all our beliefs are false. The skeptic’s point is simply that we have no fail-safe method for determining when our beliefs are true or false. Given this circumstance, the skeptic will argue that we cannot distinguish the situation of having evidence that leads to true beliefs from the situation of having the same sort of evidence plus a universal belief falsifier, which leads to false beliefs. Obviously, the skeptic believes that nothing is beyond doubt.
For any one of our beliefs, we can imagine a set of circumstances in which it would be false. For example, I believe I was born in Rahway, New Jersey. However, my birth certificate could be inaccurate. Furthermore, for whatever reasons, my parents may have wished to keep the truth from me. I will never know for sure. I also believe that there is overwhelming evidence that Adolf Hitler committed suicide at the close of World War II. However, it could be true (as conspiracy
theorists maintain) that his death was faked and that he lived a long life in South America after the war. The theme of the skeptic is that certainty is necessary for there to be knowledge, and if doubt is possible, then we do not have certainty. We now have the considerations in place that the skeptic uses to make his or her case. There are many varieties of skeptical arguments, each one exploiting some possible flaw in either human cognition or the alleged evidence we use to justify our beliefs. Instead of presenting various specific arguments, we can consider a “generic skeptical argument. ”
Generic Skeptical Argument 1. We can find reasons for doubting any one of our beliefs. 2. It follows that we can doubt all our beliefs. 3. If we can doubt all our beliefs, then we cannot be certain of any of them. 4. If we do not have certainty about any of our beliefs, then we do not have knowledge. 5. Therefore, we do not have knowledge. Pyrrho of Elis (360–270 B. C. ), a philosopher in ancient Greece, inspired a skeptical movement that bore his name (Pyrrhonian skepticism).
Pyrrho was skeptical concerning sense experience. He argued that for experience to be a source of knowledge, our sense data must agree with reality. But it is impossible to jump outside our experience to see how it compares with the external world. So, we can never know whether our experience is giving us accurate information about reality. Furthermore, rational argument cannot give us knowledge either, Pyrrho said, because for every argument supporting one side of an issue, another argument can be constructed to prove the opposing case.
Hence, the two arguments cancel each other out and they are equally ineffective in leading us to the truth. The followers of Pyrrho stressed that we can make claims only about how things appear to us.
You can say, “The honey appears to me to be sweet” but not, “The honey is sweet. ” The best approach, according to these skeptics, was to suspend judgment whenever possible and make no assumptions at all. They believed that skeptical detachment would lead to serenity. “Don’t worry about what you cannot know,” they advised. Some skeptics distilled these arguments down into two simple theses. First, nothing is self-evident, for any axiom we start with can be doubted. Second, nothing can be proven, for either we will have an infinite regress of reasons that support our previous reasons or we will end up assuming what we are trying to prove.
Descartes began his quest for knowledge with the assumption that if he had rational certainty concerning his beliefs, he necessarily had knowledge, and if he did not have certainty, he did not have knowledge. The skeptics who came after Descartes agreed with this assumption. However, as we will see in the next section, Descartes argues that there are a number of things of which we can be certain and, hence, we do have knowledge. On the other hand, the skeptics doubt whether Descartes or anyone can achieve such certainty.
Lacking any grounds for certainty, the skeptics claim we cannot have knowledge about the real world. Thus, the skeptics think that Descartes’s arguments for skepticism are stronger than his proposed answers. Such a philosopher was David Hume, whom we will encounter later when we examine empir EXAMINING THE STRENGTHS AND WEAKNESSES OF SKEPTICISM Positive Evaluation 1. Weeding a garden is not sufficient to make flowers grow, but it does do something valuable. In what way could the skeptics be viewed as providing a “philosophical weeding service” by undercutting beliefs that are naively taken for granted?
2. The skeptics are unsettling because they force us to reexamine our most fundamental beliefs. Is it better to live in naive innocence, never questioning anything, or is it sometimes worthwhile to have your beliefs challenged? Negative Evaluation 1. The skeptics make the following claim: “Knowledge is impossible. ” But isn’t this claim itself a knowledge claim that they declare is true? Is the skeptic being inconsistent? 2. The skeptics use the argument from illusion to show that we cannot trust our senses.
But could we ever know that there are illusions or that sometimes our senses are deceived unless there were occasions when our senses weren’t deceived? 3. Some skeptics would have us believe that it is possible that all our beliefs are false. But would the human race have survived if there was never a correspondence between some of our beliefs and the way reality is constituted?
We believe that fire burns, water quenches thirst, vegetables nourish us, and eating sand doesn’t. If we didn’t have some sort of built-in mechanism orienting us toward true beliefs, how could we be as successful as we are in dealing with reality? 4. Is skepticism liveable? Try yelling to someone who claims to be a skeptic, “Watch out for that falling tree limb! ” Why is it that a skeptic will always look up? Think of other ways in which skeptics might demonstrate that they do believe they can find out what is true or false about the world. 5. Is Descartes’s demand for absolute certainty unreasonable?
Can’t we have justified beliefs based on inferences to the best explanation, probability, or practical certainty? Does certainty have to be either 100 percent or 0 percent? The answer is that our reason tells us that “something cannot come from nothing” and “material objects do not vanish into thin air. ” We will distrust our senses before we will abandon these beliefs.
Hence, our reason seems to have veto power over our sense experience. We often trust our reason even in the face of apparently solid, experiential evidence. The rationalists raise this trust in reason into a full-fledged theory of knowledge. Rationalism is a very influential theory about the source and nature of knowledge. This position may be summarized in terms of the three anchor points of rationalism. These three points are responses to the second question of epistemology, Does reason provide us with knowledge of the world independently of experience?
Reason Is the Primary or Most Superior Source of Knowledge about Reality According to the rationalist, it is through reason that we truly understand the fundamental truths about reality. For example, most rationalists would say the truths in the following lists are some very basic truths about the world that will never change. Although our experience certainly does illustrate most of these beliefs, our experiences always consist of par-ticular, concrete events. Hence, no experiences of seeing, feeling, hearing, tasting, or touching specific objects can tell us that these statements will always be true for every future event we encounter.
The rationalist claims that the following statements represent a priori truths about the world. They are a priori because they can be known apart from experience, yet they tell us what the world is like. LOGICAL TRUTHS A and not-A cannot both be true at the same time (where A represents some proposition or claim). This truth is called the law of noncontradiction. (For example, the statement “John is married and John is not married” is necessarily false. ) If the statement X is true and the statement “If X, then Y” is true, then it necessarily follows that the statement Y is true.
The area of a triangle will always be one-half the length of the base times its height. If X is larger than Y and Y is larger than Z, then X is larger than Z. METAPHYSICAL TRUTHS Every event has a cause. An object with contradictory properties cannot exist. (No matter how long we search, we will never find a round square. ) ETHICAL PRINCIPLES Some basic moral obligations are not optional. It is morally wrong to maliciously torture someone for the fun of it. Sense Experience Is an Unreliable and Inadequate Route to Knowledge Rationalists typically emphasize the fact that sense experience is relative, changing, and often illusory.
An object will look one way in artificial light and will look different in sunlight. Our eyes seem to see water on the road on a hot day, but the image is merely an optical illusion. The rationalist claims that we need our reason to sort out what is appearance from what is reality. Although it is obvious that a rationalist could not get through life without some reliance on sense experience, the rationalist denies that sense experience is the only source of knowledge about reality. Furthermore, experience can tell us only about particular things in the world.
However, it cannot give us universal, foundational truths about reality. Sensory experience can tell me about the properties of this ball, but it cannot tell me about the properties of spheres in general. Experience can tell me that when I combine these two oranges with those two oranges, they add up to four oranges. However, only reason can tell me that two plus two will always equal four and that this result will be true not only for these oranges, or all oranges, but for anything whatsoever. The Fundamental Truths about the World Can Be Known A Priori: They Are Either Innate or Self-Evident to Our Minds Innate ideas are ideas that are inborn.
They are ideas or principles that the mind already contains prior to experience. The notion of innate ideas is commonly found in rationalistic philosophies, but it is rejected by the empiricists. The theory of innate ideas views the mind like a computer that comes from the factory with numerous programs already loaded on its disk, waiting to be activated. Hence, rationalists say that such ideas as the laws of logic, the concept of justice, or the idea of God are already contained deep within the mind and only need to be brought to the level of conscious awareness. Innate ideas should not be confused with instinct.
Instinct is a noncognitive set of mechanical behaviors, such as blinking the eyes when an object approaches them. The theory of innate ideas is one account of how we can have a priori knowledge. Other rationalists believe that if the mind does not already contain these ideas, they are, at least, either self-evident or natural to the mind and the mind has a natural predisposition to recognize them. For example, Gottfried Leibniz (1646–1716), a German rationalist, compared the mind to a block of marble that contains veins or natural splitting points that allow only one sort of shape to be formed within it.
Thus, the mind, like the marble, has an innate structure that results in “inclinations, dispositions, habits, or natural capacities” to think in certain ways. In contrast to this view, John Locke (a British empiricist) said: “There is nothing in the intellect that was not first in the senses. ” In response, Leibniz tagged the following rationalistic qualification at the end of Locke’s formula, “except for the intellect itself. ” Obviously, in saying that the mind contains rational ideas or dispositions, the rationalists do not believe a baby is thinking about the theorems of geometry.
Instead, they claim that when a person achieves a certain level of cognitive development, he or she will be capable of realizing the self-evident truth of certain ideas. Leibniz pointed out that there is a difference between the mind containing rational principles and being aware of them. Rationalists give different accounts of how the mind acquired innate ideas in the first place. Socrates and Plato believed that our souls preexisted our current life and received knowledge from a previous form of existence. Theistic rationalists, such as Descartes, tend to believe that God implanted these ideas within us.
Others simply claim that these principles or ideas naturally accompany rational minds such as ours. THE RATIONALISTS’ ANSWERS TO THE THREE EPISTEMOLOGICAL QUESTIONS Section 2. 0 contained three questions concerning knowledge: (1) Is knowledge possible? (2) Does reason provide us with knowledge of the world independently of experience? and (3) Does our knowledge represent reality as it really is? While differing on the details, all the rationalists give the same answers to these three questions. First, they all believe that knowledge is possible. Generally, we are able to discern that some opinions are better than others.
For example, in the discipline of mathematics some answers are true and some are false. We could not know this fact if obtaining knowledge was impossible. Second, the rationalists agree that only through reason can we find an adequate basis for knowledge.
For example, in mathematics and logic we are able through reason alone to arrive at truths that are absolutely certain and necessarily true. Third, rationalists agree that beliefs that are based on reason do represent reality as it truly is. In the following sections, I examine three classical rationalists to see how they illustrate the three anchor points of rationalism and answer the three epistemological questions.
Socrates’ answers to the three epistemological questions should be clear. (1) We are able to distinguish true opinions from false ones, so we must know the standards for making this distinction. (2) These standards could not be derived from experience so they must be unpacked through a rational investigation of the reservoir of all truth—the soul. (3) Since our rational knowledge provides us with information that enables us to deal successfully with the world and our own lives, it must be giving us an accurate picture of reality.
However, according to Plato, since the physical world is constantly changing, sense perception gives us only relative and temporary information about changing, particular things. Being a typical rationalist, Plato thought that ultimate knowledge must be objective, unchanging, and universal. Furthermore, he argued that there is a difference between true opinions and knowledge, for our beliefs must be rationally justified to qualify as knowledge. Finally, Plato believed that the object of knowledge must be something that really exists.
Plato and the Role of Reason Do mathematical truths, such as those in the multiplication tables, exist within the mind or do they exist outside the mind? Plato would say both. If mathematical truths exist only in the mind, then why does physical reality conform to these truths? If mathematical truths are only mind-dependent ideas, then why can’t we make the truths about triangles be anything we decide them to be? The world of Alice’s Adventures in Wonderland was created in the mind of Lewis Carroll. He could have made the world’s properties be anything he decided. But obviously, we can’t make up such rules for the properties of numbers. We don’t create these truths; we discover them.
Thus, Plato would argue, these truths are objective and independent of our minds. But if they are independent of our minds, then they must refer to something that exists in reality. Although the number seven, for example, has objective properties that we discover, these properties are not physical. We do not learn the truths about numbers by seeing, tasting, hearing, smelling, or touching them. From this concept, Plato concludes that the world of mathematics consists of a set of objective, mindindependent truths and a domain of nonphysical reality that we know only through reason. What about justice?
What color is it? How tall is it? How much does it weigh? Clearly, these questions can apply to physical things, but it is meaningless to describe justice in terms of observable properties. Furthermore, no society is perfectly just. Hence, we have never seen an example of perfect justice in human history, only frail, human attempts to approximate it. Because reason can contemplate Justice Itself,* we can evaluate the deficient, limited degrees of justice found in particular societies.
Particular nations come and go and the degree of justice they manifest can rise or fall. But the objects of genuine knowledge such as true Justice or true Circularity are eternal and unchanging standards and objects of knowledge. Plato on Universals and the Knowledge of Reality Thus far, Plato has argued that there are some things that we could not know about (Justice, Goodness, Equality) if experience was our only source of knowledge.
The soul must have somehow acquired knowledge independently of the senses. But what, exactly, are the objects of this special sort of knowledge? In answering this question, Plato builds on the distinction he has made between the here-and-now realm of sense experience and the unchanging realm of rational knowledge.
He says that in the world of sense experience we find that particulars fall into a number of stable, universal categories. Without these categories, we could not identify anything or talk about particulars at all. For example, Tom, Andre, Maria, and Lakatria are all distinct individuals, yet we can use the universal term human being to refer to each of them. In spite of their differences, something about them is the same. Corresponding to each common name (such as “human,” “dog,” “justice”) is a Universal that consists of the essential, common properties of anything within that category.
Circular objects (coins, rings, wreathes, planetary orbits) all have the Universal of Circularity in common. Particular objects that are beautiful (roses, seashells, persons, sunsets, paintings) all share the Universal of Beauty. Particulars come into being, change, and pass away but Universals reside in an eternal, unchanging world. The rose grows from a bud, becomes a beautiful flower, and then turns brown and ugly and fades away. Yet the Universal of Beauty (or Beauty Itself ) remains eternally the same.
Plato believes that Universals are more than concepts, they are actually the constituents of reality. Hence, in answer to the third epistemological question, Plato believes that knowledge of Universals provides us with knowledge of the fundamental features of reality, which are nonphysical, eternal, and unchanging. Plato also refers to these Universals as “Forms. ” The following thought experiment will help you appreciate Plato’s emphasis on Universals and universal truth. Descartes on the Possibility of Knowledge Although Descartes was certain he could not be deceived about his own existence, the possibility of a Great Deceiver cast a shadow over all his other beliefs.
Unless he could find something external to his mind that would guarantee that the contents of his mind represented reality, there was little hope for having any knowledge other than that of his own existence. Descartes sought this guarantee in an all-powerful, good God. Hence, Descartes says, “As soon as the opportunity arises I must examine whether there is a God, and, if there is, whether he can be a deceiver. For if I do not know this, it seems that I can never be quite certain about anything else. ”12 If Descartes could prove that such a God exists, then he could know that knowledge is possible.
But notice how limited are the materials Descartes has at his disposal for proving God’s existence. He cannot employ an empirical argument based on the nature of the external world, for that is an issue that is still in doubt. So, he must construct a rationalistic argument that reasons only from the contents of his own mind. STOP AND THINK Descartes on the Role of Reason In the following passage from Meditation III, Descartes says the “natural light of reason” shows him that (1) something cannot arise from nothing and (2) there must be at least as much reality in the cause as there is in the effect.
• What examples does he use to illustrate each of these principles? • How does he apply these two principles to the existence of his own ideas? The argument that Descartes has given us in the previous passages can be summarized in this way: 1. Something cannot be derived from nothing. (In other words, all effects, including ideas, are caused by something. ) 2. There must be at least as much reality in the cause as there is in the effect. 3. I have an idea of God (as an infinite and perfect being). 4. The idea of God in my mind is an effect that was caused by something.
5. I am finite and imperfect, and thus I could not be the cause of the idea of an infinite and perfect God. 6. Only an infinite and perfect being could be the cause of such an idea. 7. Therefore, God (an infinite and perfect being) exists. THE THREE ANCHOR POINTS OF EMPIRICISM The Only Source of Genuine Knowledge Is Sense Experience The empiricists compare the mind to a blank tablet upon which experience makes its marks. Without experience, they claim, we would lack not only knowledge of the specific features of the world, but also the ability even to con.