Tuesday, August 3, 2010

Agnosticism Makes Knowledge Impossible

In chapter seven of Warranted Christian Belief, Alvin Plantinga discusses the epistemological implications of agnosticism - specifically David Hume's formulation of it.
I shall argue that one who displays a certain kind of agnosticism with respect to his origin and place in the universe, and also grasps a certain cogent argument, will not, in fact, know anything at all; nothing he believes will have warrant sufficient for knowledge (218).
Plantinga then reminds us that a skeptical position does not know where we have gotten our faculties from. He reminds us that when it comes to where the universe came from, Hume declares, "A total suspense of judgment is here our only reasonable resource." Not only does the agnostic not know where our faculties came from, but he does not know the exact purpose which they were designed to serve.

Given agnosticism, our cognitive faculties could have come from any number of logically possible sources:
  • We might have been created by God.
  • We might have arisen from vegetative principle.
  • We might have arise from copulation on the part of animals we know not of.
  • The list of possibilities goes on and on.
In some of these possibilities, we would have warrant for believing our faculties to be reliable, but not in all of them. Given agnosticism, we do not have epistemological grounds for discerning which possibility is legitimate and which is not. As such, Plantinga says that the probability of our faculties actually being reliable is inscrutable - or unknowable. Here is how he expresses it:
R = The Proposition that our cognitive faculties are reliable
F = The relevant facts about our faculties' origin, purpose, and provenance
P = Probability
P(R/F) is unknowable. "Another way to put it: the probability of R given Hume's agnosticism is inscrutable." Plantinga uses a story to illustrate. He suggests a scenario where our space ship lands on a distant planet and upon cracking upon the door of the spaceship we find a radio that is telling us things that we have no knowledge of (what the weather in Beijing is, whether Caesar had eggs on toast on the morning he crossed the Rubicon, whether the first human to cross the Bering Strait into North America was right or left handed, and so on). Plantinga reminds us that although this device is spitting out information, we have no grounds for believing its statements to be factual because we do not know what its purpose is, or whether it has a purpose. "You see that the probability of its being reliable, given what you know about it, is for you inscrutable."

The fact that we do not know what the device's purpose is, or whether it has a purpose is the defeater for the proposition that the device speaks the truth. We are not warranted in believing what the device is telling us, given this defeater. Plantinga then applies this to agnosticism.
Because B is just any belief I hold - because I have a defeater for just any belief I hold - I also have a defeater for my belief that I have a defeater for B. This universal, all-purpose defeater provided by my agnosticism is also a defeater for itself, a self-defeating defeater...Thus the true skeptic will be skeptical all the way down; he "will be diffident of his philosophical doubts, as well as his philosophical conviction" (226)
Skepticism is self-defeating. It is the undefeatable defeater. "That is because any doubt about our cognitive faculties generally is a doubt about the specific faculty that produces this conviction."

Even if our apologetic methodology differs from Plantinga's, even if we disagree with his arguments in God Freedom and Evil, this is a very strong argument, and one which we Van Tillians should be quick to utilize. This argument is very similar to Plantinga's argument that naturalism is self-defeating, and I plan on taking up that argument as well at some point in the future.


  1. Adam,

    Some random thoughts

    When I initially read something from Plantinga it makes sense, but I have to read it three or four more times to get why it makes sense. An example of this is Plantinga's argument about the difference between an evolutionist and an atheist.

    From 2003 thru 2008 I did an intense amount of commercial airline flying. I found an MP3 player for $40. I was able to listen to huundreds of hours of Bahnsen.

    I would very much like for the TAG argument to be developed (if it can be) concerning Christianity versus other religions. I'll include in here amongst other religions what Machen called Modernism or as he designated it in Christianity and Liberalism, "another religion."

    As for your last paragraph, every presuppositionalist uses evidences and every evidentialist has presuppositions. I agree with you, we should all that we can for our King including evidentialist arguments that work.

    Even if we might have been working with an atheist friend for a while and we bring him/her to the point of asking them, "where do the laws of logic come from?", isn't that in a sense an evidentialist question?

  2. I would also like to add that I am a presuppositionalist

  3. I guess the difference between an evidentialist and a presuppositionalist, in my mind, is that the evidentialist is willing to meet the atheist on his ground - to meet him in his unbelief and show him that God can live up to his unbelieving standards.

    Every argument is in a sense evidentiaist if by evidentialist you simply mean "giving arguments for the faith." Even Bahnsen is an evidentialist by that standard.

    See, although Plantinga may be approaching this question of agnosticism from an evidentialist perspective, he is actually dealing with a question which fits very nicely within the Transcendental approach to apologetics. Because we go to the agnostic and say, "Your agnosticism is no safe haven from criticism. Given your own beliefs, consistently held, you cannot claim to have warrant to believe anything. You cannot know anything. The Christian worldview can account for the preconditions necessary for knowledge, but atheism cannot and neither can your agnosticism, which you thought was so safe from criticism. You may not claim to have knowledge and be consistent with your own worldview. By borrowing the Christian approach to knowledge and truth and the reliability of our senses, you prove it to be true by your actions, even while denying it by your words."

  4. Adam,

    You might enjoy this

    It is advertised as a debate but it came across more as a hearty discussion between friends

    The third MP3 is not part of it but it is Bahnsen discussing what was just presented

    I think I'm going to re-listen to this. Its been a while

    BTW, thanks for the hard work you put in here

    &, I just picked up Marsden's bio of Edwards. How are you enjoying it?


  5. You know, the Marsden bio is great because it gets as much into theology as it does biography, which you don't always get a lot of.

    My only disappointment so far is that I'm about 40% through the book, and I've only just gotten to the part of the book where Edwards is the Pastor of the church. It's remarkable to think about how much of life is actually spent getting ready for the rest of it.

  6. "It's remarkable to think about how much of life is actually spent getting ready for the rest of it."

    Moses, Joshua, & Paul under Gamaliel

    God trains His leaders

    & we need a trained leadership.

    I'm only a deacon in a NAPARC church


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