EMPIRICISM

For the empiricists, experience is the primary source of our knowledge and the proper test of truth is external. Our ideas are true only if they relate to our findings of the external world. They believe the mind is a blank slate, called "tabula rosa" by the Greeks, at birth, or "a white paper, void of all characters," in which experience only can provide it with ideas. Empiricists further maintain that the acquisition of knowledge is slow and self-correcting, limited by the possibilities of experiment and observations. Hence, our knowledge is based off of a posteriori propositions, derivable with the help of sense experience. Finally, empirical knowledge is inductive in character, starting with a conclusion and attempting to prove it by premises. The premises may be true and the conclusion still false though.

The three principal philosophers who may be called Empiricists without doubt are: John Locke, David Hume, and George Berkeley. For the purposes of our discussion, the first two will be scrutinized.

JOHN LOCKE

The principal belief in Rationalism is in the existence of innate ideas, or ideas we have at birth. Locke automatically said that these innate ideas do not exist. He said there is no idea that all men have and no principle that all men accept. As well, we cannot have an idea from any other source but sensation or reflection. Ideas of sensation are arrived at by way of the object stimulating one of our sensory organs. Ideas of reflection are those we get from observing the operation of our own mind as it is used to reason, believe, know, and remember about ideas we already have. Knowledge is gained through the perception of a relationship between ideas.

Locke said that the only types of knowledge we can have is that of sensations and reflections, which yield simple ideas. Complex ideas are formed by the repetition, comparison, and combination of these simple ideas. There exists three types:

1. modes - a complex idea of something that is not thought of as existing by itself, but as being dependent on a thing or a substance.
   
2. relations - a comparison of ideas.
   
3. substance - a complex idea about the pure substance that supports our ideas about particular substances; formed by a combination of ideas plus something else.
   

Locke said that men are capable only of a knowledge of the agreement and disagreement of their ideas through identity, diversity, and coexistence.

Next, we can discern certain qualities that objects have. They are ideas produced in the mind by an object and are of two classes:

1. primary qualities - resemble the object that produced them and include solidity, extension, figure, motion, rest, and number.
   
2. secondary qualities - do not resemble the object that produced them and include color, taste, sound, heat, and cold.
   

Locke also identified three degrees of cognitive adequacy:

1. intuitive knowledge - immediately certain and cannot be doubted; the mind sees a necessary connection; this is the knowledge of our own existence.
   
2. demonstrative knowledge - we have a connection that we do not see immediately but that we come to know by finding a series of subconnections which are seen immediately; this is the knowledge of God.
   
3. sensitive knowledge - many ideas between which are no necessary relations to be seen; this is knowledge of other people and physical things.
   

Finally, Locke left himself open to criticism by suggesting a world we could know only through our ideas and consisting of things held together by mysterious, unknowable substances. The question is raised of how we can know that which is unknowable and how we could possess any knowledge that such a thing exists?

DAVID HUME

David Hume agreed with his predecessors, Locke and Berekely, but carried their ideas farther. He said impressions are all the sensations, passions, and emotions that we experience. Ideas then are copies of these impressions and differ from them only in that ideas are faint and impressions are vivid. We remember impressions, the primary data of our knowledge, by "faint images" or ideas of them. The ideas may be either simple, resembling their antecedent impression, or complex, formed by means of various operations and made up of simple ideas. For example, a centaur is a complex idea made up of the simple ideas of a man and a horse. There are some words that cannot be shown to have any antecedent impressions, such as with the word substance.

We know nothing of an external world and so we cannot know the origin of our impressions. We can only know the ideas and impressions. We believe in an external world but cannot justify these beliefs since no logical explanation can be given. For this reason metaphysics is impossible.

Hume supposes the existence of two types of knowledge that we can have. First, relations of ideas are arrived at by logical reasoning. This incorporates the discipline of mathematics. Matters of fact are arrived at by observation. Reasoning here is not as certain as in the former since it is grounded in empirical fact and does not rely upon logical reasoning. For example, when you hear a phone ring you naturally reason that a person is on the other end. We distinguish between sheer coincidence and real causation and conclude that the cause necessitates the effect. Some type of necessary connection exists between the two. Due to this, we can predict that the next time A occurs B will follow.

But Hume asks what is this causal relationship or necessary connection? All we ever observe is the constant conjunction of two events in time, following from one another. Since this is all we observe, this is all we should admit. Then, if time and contiguity are all we observe, where does this idea of causal bond come from? Hume says it comes from custom or habit. By always observing B follow from A, we, by habit, assume this conjunction.

He concludes that since a large part of our study of matters of fact depend on causal relations, our knowledge must be regarded as both limited and uncertain. Hume branded an extreme form of intellectual skepticism. We cannot be sure of the existence of self, an external world, or the law of cause and effect.

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