What an impact a true Christian can be.
Vodpod videos no longer available. “How much do you have to hate sombody to NOT proselytize?”
December 20, 2008
December 16, 2008
In an effort to avoid skepticism, Fred Dretske advocates the rejection of closure; the epistemic principle that asserts that knowledge is closed under known entailment. Thus, if S knows P and S knows that P entails Q, and S comes to believe Q on the basis of this entailment, then S knows Q. Dretske asserts that we have only two choices in regards to knowledge: one is that we retain closure and accept skepticism concerning ordinary knowledge that we take for granted (I have hands, etc.), the other is that we deny closure and keep ordinary knowledge (Dretske, 23). According to Dretske, the denial of closure is the most reasonable choice. John Hawthorne disagrees with Dretske and argues in favor of closure because he believes the denial of closure leads to more serious implications than any of the other options available.
Why does Dretske think that closure demands skepticism? Consider the following example:
Yet can Sarah actually know that what she sees is not a scarecrow? Has she taken the time to walk to the field and observe what she takes to be a farmer to make sure that she has not been deceived? And if Sarah does not know if she is looking at a scarecrow, then she cannot know that there is a farmer in the field: P à Q, ~ Q, therefore ~ P. Indeed, it seems that possession of ordinary knowledge seems to presuppose the knowledge one is not being deceived, which Dretske refers to as protoknowledge (14). However it seems highly unintuitive for Sarah to claim knowledge of Q without any evidence. Thus skepticism prevails.
One may ask why Sarah does not have evidence of Q if she has evidence of P. Consider the evidence that constitutes knowledge of P: Sarah sees the farmer standing in the field (maybe he is waving his arm, or is bent over engaging in a hoeing motion), and due to her past experience with such perceptions, she formulates the belief that she is indeed seeing a farmer in the field. Yet Sarah’s evidence for P is not transmissible to Q. She cannot know that she is being deceived by a robotic scarecrow by simply looking at the distant field; such knowledge would require different evidence. This problem is further magnified with the introduction of Dretske’ “heavyweight implications” (Cartesian demons, brains in vats, etc.) that are impossible to determine through appeal to perception. Thus, Dretske argues that the principle of closure decimates any hope for ordinary knowledge, for as long as I cannot know that I am not a brain in a vat being systematically deceived through the machinations of a mad scientist, I cannot even know that I am sitting at a computer writing this paper.
Dretske considers the aforesaid “heavyweight implications” to be damning to ordinary knowledge if closure holds and leaves us with a choice between (1) skepticism with closure or (2) ordinary knowledge without it. Dretske chooses the latter. Thus Sarah can know that she sees a farmer in the field and know that this entails that she is not seeing a scarecrow, yet still not know that she is not seeing a scarecrow.
Hawthorne argues against Dretske, not so much by offering a solution to the problem of closure, but by pointing out that the denial of closure leads to greater problems than it proposes to solve. One such problem is that the denial of the intuitive principle of closure leads to the denial of the even more intuitive principle of distribution as well (Hawthorne, 31-32). Whereas closure is bases upon logical entailment, distribution is based upon logical equivalence. Thus the proposition “there is a farmer in the field” is equivalent to the conjunction “there is a farmer in the field and it is not the case that there is not a farmer in the field but an animatronic scarecrow instead”. Thus, according to distribution, Sarah is in a position to know “that it is not the case that there is not a farmer in the field but an animatronic scarecrow instead”. However, it is incredibly difficult to see how one can know the conjunction of P and Q but not know Q. Indeed, Hawthorne demonstrates that the rejection of closure is not nearly as appealing as Dretske claims.
Yet, as previously mentioned, Hawthorne does not resolve the problems inherent in retaining closure. He even goes so far as to present his own closure implied quandary in his “Misprint” example (39). To restate the puzzle: I know from reading the newspaper that the Panthers defeated the Packers last Sunday. This, in turn, entails that it is not the case that the story was a misprint and it was the Packers who actually defeated the Panthers instead. However, it seems incredibly odd to say that I know that there was not a misprint because I know that Panthers won because I read the paper. This is like telling a skeptical friend “If you don’t believe me just ask me!”
Hawthorne gives Contextualism as a possible resolution to the problem of closure but readily admits the problems inherent in this view (one of which is that philosophers should rank among the most ignorant people in the world due to their understanding of skepticism!). Hawthorne – as well as Dretske’s response – leaves us with the following type of concept: “All the options are bad, but we have to pick the one that seems the most intuitively plausible.” Dretske thinks the denial of closure is the most plausible while Hawthorne argues that doing so leads to more implausibility than not.
I agree that both horns of Dretske’s dilemma (23) are unpalatable, and I think that neither philosopher presents a compelling solution to the problem of closure; however I am more willing to accept skepticism than to deny the principle of closure; especially since denying closure appears tantamount to denying logical equivalence as well. Indeed, it is my regard for logic that compels me to side with Hawthorne. It seems as though the denial of closure comes very close to a denial of logic and I cannot comprehend how it is possible that I can know P à ~ P yet not know ~ P. Like Dretske and Hawthorne I have no compelling solution to the problems that closure presents (although I sincerely hope to discover one or discover someone who has), but I certainly think that the grass is greener on Hawthorne’s side of the fence.
March 18, 2008
A Message from
To me this one is worth re-posting for WOTM.
January 31, 2008
In pursuit of a mind untroubled by bothersome knowledge, Pyrrhonian skeptics, such as Sextus Empiricus, employed various arguments designed to bring about suspension of judgment. One such argument is to be found in the second of the Five Modes of late Pyrrhonism. Sextus presents this argument in the fifteenth chapter of his Outlines of Pyrrhonism.
The mode based upon regress ad infinitum is that whereby we assert that the thing adduced as a proof of the matter proposed needs a further proof, and this again another, and so on ad infinitum, so that the consequence is suspension [of judgment], as we posses no starting point for our argument.
The argument could be rendered thus:
1. For any given belief, a proof is required for that belief to be justified (assumed).
2. However, for every proof given, yet another proof is required for that proof to be justified; leading to vicious infinite regress of proofs.
3. An infinite regress of proofs provides no basis for justification since it is impossible to determine if every belief in the series is justified.
4. Therefore, it is impossible to justify any given belief and so one should suspend judgment.
Sextus goes on to anticipate and reject two possible solutions to the problem of an infinite regress: these are expressed in the fourth and fifth modes, in which the former is concerned with circular reasoning and the latter is concerned with hypotheses (assumptions of knowledge).
As to the initial argument, it does appear to be valid given the skeptic’s criteria of justification. Furthermore, the third premise seems to be quite self-evident. It does not seem possible to provide individual justifications for an infinite series of beliefs; at least, not in a finite measure of time (which would unfortunately describe the lifespan of all known human beings). A criticism of the argument must therefore focus upon the first two premises, both of which are based upon a certain assumption of justification.
Adopting circular reasoning would be one way of rejecting the second premise. As stated above, Sextus anticipates this objection in the fourth mode:
The Mode of circular reasoning is the form used when the proof itself which ought to establish the matter of inquiry requires confirmation derived from that matter; in this case, being unable to assume either in order to establish the other, we suspend judgment on both.
To illustrate the point very simply:
1. Sextus Empiricus’ arguments for skepticism are irrefutable (how do you know that?).
2. Because he is the most persuasive skeptic in history (how do you know that?)
3. Because his arguments for skepticism are irrefutable.
While this example is quite simple, it does demonstrate that circular reasoning is patently absurd. One can prove anything by begging the question. Likewise, one can justify any claim to knowledge if they are allowed to engage in a vicious circle of justifications.
Assuming a belief (hypothesis) to be true would be another way of avoiding an infinite regress. Sextus deals with this in the fifth Mode:
We have the Mode based on hypothesis when the Dogmatists, being forced to recede ad infinitum, take as their starting-point something which they do not establish by argument but claim to assume as granted simply and without demonstration.
Under this scheme, an infinite regress can be avoided by digging one’s epistemological heels into a belief that requires no justification. Sextus assumes that this position is invalid since the hypothesizer provides no argument or demonstration for the belief to which he holds. This seems to be a valid objection to a whole assortment of unjustified beliefs. Take, for example, the belief that I am Napoleon Bonaparte. Using the logic of the hypothesizer, could I not simply assert this belief firmly and with no justification? One can see why Sextus considers this position to be untenable.
What about other beliefs though? There are certainly beliefs that seem to be more reasonable that the one given above. Take, for example, the belief that I am presently sitting before my computer typing this post. Must this belief be ‘proven’ somehow before it can count as knowledge? Sextus would say ‘yes’, but there are many who would disagree with him. This leads us to examine the epistemological assumption that underlies the first premise of the infinite regress argument.
Sextus merely assumes that every belief requires some form of proof before it can be justified and count as knowledge. Deductive certainty, however, is an incredibly high standard of justification. Given his assumption, one can see how it would be impossible to know almost anything. But do we have to grant his assumption? Do we have to explain how we have knowledge of some specific thing for that knowledge to be justified? If so, would it not be reasonable to ask the skeptic how he knows that we do not have knowledge of a specific item?
It is at this point that the skeptic would probably launch into various arguments attacking the reliability of the senses; such as “How do you know that you are not dreaming?” or “How do you know that you are not insane or a brain in a vat?” However, the hypothesizer may respond that just because something is logically possible, this does not mean that it is reasonable to believe it. It is logically possible that a teddy bear is orbiting Mars or that the moon is actually made of green cheese, but this does not mean that I am required to believe these things to be so, or that it would be reasonable to do so. Likewise, it may be logically possible that I am merely dreaming that I am typing this post or that I am insane, but the skeptic must provide me with good reasons to believe these things. And I think that this is something that Sextus, for all his mighty modes, fails to provide.
Therefore, the infinite regress argument of the skeptic is as only as powerful as its underlying assumption. If deductive certainty is the required justification for knowledge, then we indeed know very little. However, if certainty is not required, then the second Mode is unpersuasive. It all depends upon who shoulders the burden of proof.