Philosophy 251 Notes

Notes on Epistemology: Empiricism I

Rationalists (e.g., Descartes) claim that real knowledge (about self, God, world) is possible only if it is certain or based on something that is certain. Since sense experience cannot guarantee certainty, it cannot be the basis for knowledge. Only reason can reveal propositions that are indubitable (i.e., cannot be doubted), so only reason can be trusted to provide knowledge (as opposed to mere beliefs).

The problem with relying on reason alone, though, is that a priori propositions (that is, propositions whose truth or falsity is known prior to and independent of any sense experience) do not provide any useful information about the world. To know, for example, that bachelors are unmarried, that unicorns have horns, or that triangles have three sides, does not tell us whether there are such things in the world as bachelors, unicorns, or triangles. For that information, we have to rely on experience. But if experience is ruled out by rationalists as unjustified bases for knowledge, then it seems that we will never be able to know anything about the world.

Descartes tries to get around this problem by saying that we know that we exist, and that is some information about the world that is not based on sense experience. We also know (he says) that God exists and that God does not deceive us when we limit our beliefs about the world to clear and distinct ideas. So we can know things about the world insofar as it is clearly and distinctly organizable. That last feature means that, if we think about things in the world not in terms of what we learn from relying on our senses (e.g., that grass is green, or that it is cold outside) but only in terms of how things have to be (e.g., that in order to be grass, a plant has to have certain characteristics), we will then be able to say that we know something about them. Otherwise, we have to admit that we have beliefs about things, not knowledge.

Such a conclusion simply seems wrong to those who think that we are justified in trusting sense experience as the source of knowledge. Such thinkers are called empiricists (from the Greek empeiria, experience) because they claim that all knowledge of things in the world is based ultimately on experience, not on the purely mental operations of reason alone. For empiricists, facts about the world are known a posteriori (that is, they depend on experience for their truth or falsity), are publicly verifiable, and exhibit enough order that they can be the basis for generalizations and predictions. Admittedly, experience does not provide the absolute certainty that rationalists require for saying that you know something. But even if our knowledge is only probable, at least it is of some use (rather than being simply about how we understand definitions).

I. Aristotle (384-322 BC): Like Plato, Aristotle says that a thing (or "substance") is what it is and is known to be that thing in virtue of its "nature" or "essence" (what Plato calls a "Form"). But Aristotle argues that, rather than thinking that the things we ordinarily experience are imitations or copies of what is really real (i.e., a Form), we should think that the things we normally experience in the world are themselves ultimately real. Our knowledge of the world is therefore ultimately based on our experience, not reason alone.

For Aristotle, the essence of a thing (e.g., a dog's dogness) is what makes it be that kind of thing. Dogness is found in all dogs and thus can be called a "universal." Universals do not exist apart from actual things in the world, and they can be known only by experiencing actual individual things. If all dogs were to die, the universal would no longer exist. It is in virtue of the universal that we know about dogs by knowing them in terms of their essence. But that knowledge is available only when we generalize or "abstract" the universal from our experience.

Aristotle's emphasis on using experience as the basis for knowledge is typical of an empiricist epistemology.

II. John Locke (1632-1704) is a more explicit example of an empiricist. He denies Descartes' claim that we are all born with certain innate ideas (e.g., self, God) or beliefs (e.g., A is identical to A, something cannot be and not be at the same time in the same respect). Using Ockham's razor, we should adopt the simpler explanation that we learn these things through experience or through thinking about what we experience. We start out at birth with a "blank slate" (tabula rasa), and through experience we learn how and what to think about the world.

Through experience we accumulate ideas. Some of our ideas are simple: that is, they cannot be analyzed into anything simpler. For example, our ideas of cold, hard, solid, white, space, motion, figure, thinking, willing, pleasure, pain, power, existence, unity, and succession are simple ideas. Complex ideas are formed by the mind when it repeats, compares, or unites simple ideas. Complex ideas are either compounds of simple ideas (e.g., beauty, gratitude, a man, army, universe, sugar), relations of ideas (e.g., wife, heavy), or abstractions (e.g., humanity). For Locke, abstract general ideas do not exist neither apart from the world or the mind (as Platonic Forms), nor are they essences in things (as Aristotelian universals). Rather, they exist only as concepts in our minds that identify a characteristic common to a number of things that we give labels such as "human nature" to. Ultimately, though, only individuals actually exist.

Representative Realism: Since we know only our ideas, it is important to understand them well. Some ideas represent things in the world truly, exactly as those things are apart from how we perceive them (e.g., solidity, extension, figure, motion, number--the "primary qualities"). Other ideas occur in our minds as a result of their being caused by primary qualities (the figure or motion of insensible particles such as atoms or molecules). These ideas (of what Locke calls "secondary qualities") do not represent things in the world as they are; they only appear to us that way (e.g., as colors, sounds). As long as we limit claims about the world to ideas of primary qualities, we can rely on our experience for knowledge.

Some features of Ideas: (A) Simple vs. Complex: simple ideas cannot be analyzed into simpler elements (e.g., solidity, motion). Complex ideas are compounds of simple ideas (e.g., beauty, army, man, universe), ideas of relations (e.g., larger than), or abstractions (e.g., blueness). (B) Particular vs. General: general ideas identify a characteristic common to a number of things abstracted from place and time (conceptualism), but they do not exist innately or independently (Platonic Forms).

Substance is what gives the complex of qualities an identity and supports the qualities. Unfortunately, we do not experience substance; we can only infer that something must exist that supports the qualities (so that there is something that the qualities are qualities of).

III. George Berkeley (1685-1753): We know as real only what we experience, and we experience only our ideas. Therefore, for something to be real means that it is the object of some experience: the being of things consists in their being perceived ("esse est percipi": to be is to be perceived).

There are several problems with Locke's account:

According to Berkeley, natural patterns of sense data and convention (naming) identify things. Language allows us to associate intersubjectively: even though we may not experience the same things, we learn to associate the words with whatever we individually experience. That is, we can say that we see the same thing only because we share a language in which our different ideas are related to one another.

Since sense data are not caused by material substances, they must be caused by a God who orders sense data. But like my own soul, God is not perceived but is a perceiver. So we have to modify our understanding of Berkeley's position: to be is to be perceived or to perceive.