In the last two posts, i outlined first the “broad strokes” of what falls under the realm of epistemology, followed by a look at some Greek responses to knowledge. Now, our focus jumps nearly two millenia to the next “big thing” in the history of epistemology: Correspondence.
In his Meditations on First Philosophy as an attempt to prove God’s existence concludes two things with regards to knowledge: it must both be foundational and correspond. Knowledge is true if and only if a person’s perception matches (or corresponds to) the external world. Descartes gets to these conclusions by first being skeptical about everything (so he says). He reasons that if he finds something that he cannot doubt, then he can build up an entire system of knowledge that (ultimately) proces the existence of God. Descartes first reasons that he could be dreaming (sometimes called the Dream Hypothesis), so he concludes that anything perceptible is suspicious. Keeping with his plan, he rejects perception as a basis for knowledge. In his second meditation, Descartes argues that if he is supposing that all perceptions are false, then he must somehow exist (yes, this is where he gives he famous cogito ergo sum). But, he could be deceived. So, he supposes that that some being with powers on par with God has deceived him (this is called the Evil God Scenario by some) on everything (including that which he removed via the Dream Hypothesis). But still, Decartes is still thinking. The next logical step is that he perceives himself and this must be true because he exists. Therefore, whatever he can “clearly and distinctly perceive” must be true (this is his response to the DH). Descartes then proceeds through the 3rd, 4tf, and 5th meditations arguing God’s existence on these two bases. His final conclusion is that God, a perfect being, exists and does not decieve (and thus negates the EGS). Therefore, since God does not deceive and is the source of perceptions (God is the vehicle through which perceptions are made), what is perceived must also exist. Thus, Descartes concludes that what one perceives corresponds to reality and, as such, must be true. One way of seeing this is:
In a relatively short time frame after Descartes, George Berkeley, a Bishop and professor, brought forth his ideas on human knowledge, which showed some of the difficulties with Descartes’s theory. One of Berkeley’s primary arguments against Descartes dealt with correspondence and perceptions. Essentially, one only perceives one’s own sensations. That is, all perceptions a person experiences comes from the person. This leads Berkeley to conclude that an external world (if it exists) cannot be verified. As such, there cannot be any correspondence between an internal concept/perception and an external object. Therefore, Berkeley concludes that for something to be true, it must correspond with an idea within the self. This would look like such:
Following Berkeley’s motion, Hume took the most extreme position for his day by rejecting even Berkeley’s idea. Where Berkeley was satisfied with knowledge being an internal correspondence, Hume still wanted a better definition. Hume’s main problem was that of cause and effect. He proposed that cause-and-effect was just a custom. No matter how often something came before another (such as lightning before thunder), there was no guarantee that it would be such in the future. Because of this, there isn’t anything available for an internal correspondence because every instance of something must be taken as a new object, instead of a recurrence of an prior object. There cannot be any internal correspondence. As such, Hume saw no other possible criteria for truth other than custom (or tradition).
Since Hume, very few philosophers have accepted the idea of correspondence when it comes to epistemology as a foundational criteria of it. Of course, it should be noted that Plato had already come to this conclusion centuries before (see the second post in this series), so it could be argued that, except for this small period of time, correspondence has never been a criteria for knowledge (let alone true knowledge), even though some philosophers have found ways of incorporating it in remarkable ways.