The blog of Dr Glenn Andrew Peoples on Theology, Philosophy, and Social Issues

Episode 013: Plantinga and Presuppositional Apologetics part 2


Here’s Episode 13, which is part 2 of my coverage of Plantinga and presuppositional apologetics.

In this episode I present Alvin Plantinga’s Evolutionary Argument Against Naturalism. I then close by summing up the similarity between Plantinga and Van Til and co., and respond to one objection that is common to them both.

Also, for the first time ever – we have mail! I reply to it at the end of this episode.


Hitchens vs McGrath – Finally!


Fales fails to fault Plantinga on warrant


  1. Kenny

    Not bad. Although I do have a quibble. You are right that the conclusion of Plantinga’s argument does not entail that atheists in general don’t know anything. It does entail, however, that atheists who both believe NE and understand Plantinga’s argument do not know anything, since the conclusion is that all such atheists have a defeater for all of their beliefs (and defeaters are things that rob beliefs of warrant – i.e. things that prevent beliefs from being items of knowledge).

  2. I don’t think so. Recall that Plantinga is a reliabilist. If belief forming structures are working reliably, then whether we believe or know that they are or not – they still bestow warrant. So even if we have a defeater for any belief that we hold, we can still have warrant for those beliefs.

  3. Kenny

    Plantinga is not a reliabilist (he would deny the label). He is a proper functionalist. He gives examples specifically designed to show that a belief’s being reliably formed is not sufficient for its having warrant. He also holds that our design plan specifies a defeater system. And defeaters are, by definition, things that rob our beliefs of warrant. So if one has a defeater for a belief, that belief is not an item of knowledge.

  4. In every sense that’s relevant here, Platinga’s approach is indistinguishable from reliabilism, as far as I can tell. But if you’d prefer a change in terms, Plantinga’s view entails that if our belief forming faculties are functioning properly in an environment to which they are suited and in which they are designed to work, then we have warrant for the beliefs they produce.

    Moreover, Plantinga certainly does not hold that a defeater for a belief always robs a belief of warrant. He flatly denies that view, for example, when he says that even if a Christian is presented with defeaters for their Christian beliefs, it’s possible that he/she might have an “intrinsic defeater defeater” as Plantinga calls it. In this case, that defeater defeater consists of warranted beliefs that we hold because of our proper functioning belief forming faculties. Such beliefs may have more warrant than our defeater for them. That means we’d have to do something about this defeater, and if (as we are hypothesizing), the naturalist agrees with Plantinga’s argument, the only way to do this is to give up NE.

    Incidentally, I am far from alone (and in my view, far from being mistaken as well) in seeing Plantinga as a reliabilist. For example, this review. That he criticises some reliabilist models doesn’t make him an opponent of reliabilism.

  5. Kenny

    Hey Glenn,

    First, my disagreement here notwithstanding, I want to stress that I have really been enjoying these podcasts. There needs to be more of this kind of thing (there’s so much good Christian analytic philosophy these days that the larger Christian community is almost entirely ignorant of; it needs to be made more widely known through venues like these). Keep up the good work!

    Regarding the issue of whether it’s proper to refer to Plantinga as a reliabilist, you are correct that a lot of people do refer to Plantinga as such. But, for what it’s worth, Planting himself rejects that label. I think that this is a largely a mere matter of terminology though. So the issue is not worth pressing. What is worth keeping in mind, however, is that Plantinga flatly denies that a belief’s being formed reliably is either sufficient or nearly sufficient for warrant.

    Concerning the issue of defeater defeaters, you are right that Plantinga (as well as everyone else who talks about defeaters in fact, so far as I know) maintains that there are such things. But a defeater defeater (as I understand it – I am open to being corrected on this point) is not something that prevents something that continues to be a defeater from robbing one’s beliefs of warrant. It is rather, something that prevents a potential defeater for one’s belief from being a defeater in the first place or something that prevents what has been a defeater for one’s belief from continuing to be a defeater.

    But in any case, we can sidestep the above issue about defeaters for purposes of the present discussion. Plantinga explicitly states that if one has an undefeated defeater for belief then (truth-aimed) proper function calls for the rejection of that belief (or in the case of a “partial defeater”, the holding of that belief less strongly) (see WPF pp. 40-42 and WCB pp. 359-363). And the conclusion of Plantinga’s EAAN is that the atheist who believes NE (and has understood Plantinga’s argument up to that point) has an undefeated defeater for every one of her beliefs. So, given Plantinga’s views, the conclusion of Plantinga’s argument entails that atheists (who understand Plantinga’s argument and) who continue to maintain any given belief while believing NE (including their maintaining belief in NE itself) are not functioning properly with respect to their holding that belief. And given Plantinga’s conditions for warrant, this further entails that no belief that such an atheist has is warranted — i.e. that that atheist doesn’t know anything (or at least precious little, since Plantinga might be willing to back off and concede that there are some beliefs – e.g. one’s first-person belief that one exists – that simply aren’t subject to defeat).

  6. Kenny, the claim that I deny is “And the conclusion of Plantinga’s EAAN is that the atheist who believes NE (and has understood Plantinga’s argument up to that point) has an undefeated defeater for every one of her beliefs.”

    I don’t see how the EAAN concludes that the believer in NE has an *undefeated* defeater. My reply is still that given externalism (a safer term than “reliabilism,” given the controversy of terminology), the defeater (perhaps I should call it a potential defeater) may well be defeated, so it’s not an undefeated defester at all.

  7. Kenny

    Plantinga’s own words are:

    “The devotee of N&E has a defeater D for N&E – a defeater, furthermore, that can’t be ultimately defeated; for obviously D attaches to any consideration one might bring forward by way of attempting to defeat it. If you accept N&E, you have an ultimately undefeated reason for rejecting N&E: but then the rational thing to do is to reject N&E” (Warrant and Proper Function, p. 234).

    Granted, he doesn’t say explicitly here that the naturalist has an undefeated defeater for R (the proposition that human cognitive faculties are reliable) . But I think the immediate context of the quote that I gave makes it clear that the above conclusion depends on the conclusion that the naturalist (who has understood Plantinga’s argument) has an undefeated defeater for R as long as she continues to believe N&E. For if it weren’t the case that the naturalist didn’t have an undefeated defeater for R, Plantinga’s conclusion here wouldn’t follow.

    Recall that the defeater Plantinga says she [the naturalist] has here is an undercutting defeater not a rebutting defeater. He is arguing that the probability of R on N&E is low or inscrutable, not that N&E logically entails the denial of R. One can have a defeater defeater for an undercutting defeater (say that five times fast!) without giving up the belief that constitutes (or would have constituted) that defeater. E.g. I believe the table is red. But then I find out it has red lights shining on it. So I have an undercutting defeater for my belief that the table is red. But then someone who I know to be reliable claims that they have seen the table in regular light and that it is indeed red. That gives me a defeater defeater for the undercutting defeater I had. But I can have that defeater defeater while continuing to believe that the table has red lights shining on it. Likewise, if the naturalist had a defeater defeater for the undercutting defeater for R that her belief in N&E would have otherwise furnished her, she could continue to rationally believe N&E. The mere fact that, had she lacked such a defeater defeater, N&E would have constituted a defeater for R does not rationally require her to give up her belief in N&E in order to maintain R – not any more than I am required in the above scenario to give up my belief that the table has red lights shining on it in order to maintain my belief that the table is red.

    Another parallel: Suppose as a theist my belief that there is evil in the world would have constituted an undercutting probabilistic defeater for my belief in God were it not for the fact that God furnished me with some sort of defeater defeater (say by revealing himself to me in some special way). From the mere fact that my belief that there is evil in the world would have constituted such a defeater, it doesn’t follow that in order to rationally believe in God I have to give up the belief that there is evil in the world

    Now of course, if she gives up her belief in N&E, then she no longer has an undefeated defeater for R. But as long as she continues to believe N&E she does have such a defeater, and thus she has an undefeated undercutting defeater for all of her beliefs. I.E. provided she continues to believe N&E, she doesn’t know anything (of course, given Plantinga’s views, that doesn’t entail that her beliefs aren’t true or reliably formed – but according to Plantinga’s view, a belief’s being true and reliably formed isn’t sufficient for its being an item of knowledge).

  8. Or the Naturalist may go into a diachronic loop of believing N/E defeated, which makes him lose his belief in N/E, which causes him to embrace R, which causes him to believe N/E again, ad infinitum. Then N/E would not be ultimately defeated.

    Or something like that.

    (Good to see you again Kenny)

  9. Phil, that’s something like what I have in mind, actually. He really does have a warrant for the beliefs he holds, because of the validity of proper functionalism. And then he’s faced with the potential defeater, giving rise to doubt and hence a lack of knowledge. But then he reflects on the strength which which he believes that his beliefs are warranted, a strength generated by his proper functioning faculties. So he decides that he must be mistaken in denying R. And so forth.

    Kenny, my position is that if Plantinga thinks that his argument implies that any atheist who grants his argument has a successful defeater for all of his beliefs that always removes warrant for all his beliefs, then Plantinga’s mistaken. The warrant generated by his proper functionuing belief forming faculties assure him that there must be a problem witht he defeater.

    I think….

  10. Kenny

    That’s right Phil. Plantinga talks about that just before the portion I quoted.

    Good to see you too! I still should be studying for comps rather than doing this. Oh well, I’ll stop procrastinating tomorrow!

  11. Kenny


    I think the conclusion of Plantinga’s argument follows from his premises only if it has the structure I claim it does.

    That being said, I think, for the reason you suggest, there is a potential problem with Plantinga’s argument here. Perhaps the design plan calls for the naturalist to stubbornly hold and confidently hold on to R in spite of discovering that it is extremely improbable on the rest of her beliefs (in fact, it seems plausible to me that this is what our design plan calls for when we are faced with arguments for global skepticism). But if that’s so, then Plantinga’s argument doesn’t furnish her with any defeater for R and thus no defeater for N&E.

    I actually think that the argument of Plantinga’s that you gave in the previous podcast is the stronger argument.

    Anyway. I need to stop this. I should be studying right now.

  12. I’ll let you stop now Kenny 😉

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