6.07.2007

Is Knowledge Closed Under Known Logical Implication?

Closure is the epistemic principle that for any propositions p and q, if someone knows that p, and that p entails q, then that individual is in an epistemic position to know q – that individual has sufficient evidence to know q. In other words, were that individual to believe q on the basis of her knowledge that p and that p entails q, she would thereby know q. The basic idea is that we can add to what we know by deducing things from what we already know. Such a principle seems obviously true and denying it appears to be an extravagant cost to any epistemological theory. Nonetheless, closure has been under attack in recent literature in epistemology. Closure has principally been denied as a way of avoiding skepticism. The skeptic cannot get to the conclusion that I do not know that I have hands, even if I do not know that I am not radically deceived by an evil demon, if closure is false (if it is false that we have knowledge of known entailments of what we know).

Fred Dretske gives a case like the following as a purported counterexample to closure. Joe goes to a cage marked ‘zebras’ at the zoo. Joe looks at the striped animals in the cage and believes they are zebras. In fact, it seems that Joe knows that they are zebras. For an animal to be a zebra, it cannot be a cleverly disguised mule. In knowing what a zebra is, Joe knows this fact as well. Does Joe know that the animals before him are not cleverly disguised mules? Dretske says no, and he claims that this is the intuitive answer. In supporting this claim, Dretske states that all of Joe’s evidence in favor of the animals being zebras has been neutralized and does not count in favor of the animals not being cleverly disguised mules, since Joe would have the same perceptual evidence in that case as well. In this case, (a) Joe knows there are zebras before him, and (b) Joe does not know that these are not cleverly disguised mules, even though (c) Joe knows that if an animal is a zebra then it is not a cleverly disguised mule. If (a) through (c) hold, then this is a counterexample to the closure principle. [for the contemporary relevance of this example see this].

However, (a) through (c) do not hold in the above example, this is not a counterexample to closure. Several objections can be brought to Dretske’s account. First, Joe’s evidence that there is a zebra before him is also evidence that there is not a cleverly disguised mule in front of him. Dretske seems to assume that Joe’s evidence for the former claim is solely his perceptual experience, but this is a mistake. Joe will not be justified in believing that there is a zebra before him without further background evidence regarding the nature of zoos, zookeepers, and the difficulty in so disguising a mule (that zoos are not in the buisness of trickery, that zoos often have actual zebras, etc.). Without such background evidence that is assumed in the case, it is false that Joe is justified in believing that there is a zebra in front of him. This can be seen by imaging a case where Joe has the same perceptual experience as of a zebra, but is in a context completely unfamiliar to him. In such a case it is far from clear that Joe knows that there is a zebra before him.

However, when coupled with the relevant background evidence, Joe’s perceptual evidence is also evidence that there is not a cleverly painted mule before him. Considerations concerning the nature of zoos, zookeepers, and the difficulty in disguising a mule, make the belief that there is a zebra before him the belief that Joe epistemically ought to have. What more is needed for knowledge? Joe’s belief is justified, true, and not subject to any Gettier considerations. Therefore, if this evidence is good enough for Joe to know that there is a mule before him, it is also good enough to know that there is not a cleverly disguised mule before him. Thus, closure is preserved.

Dretske might reply that a child lacks this background evidence, yet still knows that the animal before her is a zebra. If one lacked this background evidence, then one would not be justified in believing (and thus would not know) that the animals were not cleverly disguised mules, but in such a case the individual would also not know that there were zebras before her. It is by no means clear that a child in such an epistemic situation actually knows that there is a zebra before her. Even if the child can distinguish between ‘is a zebra’ and ‘merely looks like a zebra’ without the relevant background evidence, she has insufficient reason to affirm that the animal is a zebra. In addition, even if it is granted that the child knows that the animal is a zebra, it is doubtful that she can draw the inference regarding cleverly disguised mules, and if she cannot do so, then the case does not bear on the closure principle.

Second, the intuitions that Dretske appeals to do not support a denial of closure. Though people typically do claim to have seen zebras in the zoo, and though when confronted with the possibility that what they saw was actually cleverly disguised mules these people may deny that they know that what they saw was not cleverly disguised mules; when this denial is made, the former self-attribution of knowledge is often withdrawn, at least temporarily. This response is the response dictated by the closure principle. It seems that at no one time do individuals claim knowledge of a proposition and simultaneously deny knowledge of one of that propositions known entailments. As such, intuitions are on the side of closure, not against it. We have not been presented a counterexample to the closure principle.

28 comments:

Anonymous said...

motivate modification herts exposure cognition challender victims lays citizen countrys schneider
servimundos melifermuly

Anonymous said...

[B]NZBsRus.com[/B]
Dismiss Idle Downloads Using NZB Downloads You Can Swiftly Search Movies, Games, MP3s, Software and Download Them at Electric Rates

[URL=http://www.nzbsrus.com][B]Newsgroup Search[/B][/URL]

Anonymous said...

Possess making taste casinos? ruminate on this unripe [url=http://www.realcazinoz.com]casino[/url] leader and wing it reflection online casino games like slots, blackjack, roulette, baccarat and more at www.realcazinoz.com .
you can also discontinuation our untrained [url=http://freecasinogames2010.webs.com]casino[/url] barter something at http://freecasinogames2010.webs.com and breathe in staunch genially misled !
another distinguishable [url=http://www.ttittancasino.com]casino spiele[/url] chain of events is www.ttittancasino.com , because german gamblers, receive a imperil in free-flowing online casino bonus.

Anonymous said...

Dear Alice,

For long time I use this freeware: [url=http://www.freeflvtomp3converter.com]FLV to MP3 free converter[/url].

FLV to MP3 free converter is a free YouTube, MegaVideo, ClipShack and similar video sites to MP3 Converter and allows you to convert a video to MP3 file.

This software is fast, free, and requires no signup. All you need is a FLV Video file, and this software will extract the MP3, and give you an audio file.

So you are able to listen to your favorite YouTube tracks on every MP3 player.

You can download it for free at [url=http://www.freeflvtomp3converter.com]www.freeflvtomp3converter.com[/url].

I hope this help you.

Anonymous said...

You could easily be making money online in the hush-hush world of [URL=http://www.www.blackhatmoneymaker.com]blackhat hosting[/URL], Don’t feel silly if you have no clue about blackhat marketing. Blackhat marketing uses not-so-popular or not-so-known avenues to produce an income online.

Anonymous said...

i have a question, i hope you can answer it for me about skeptic and the basic idea of closure. I understand how the closure principle applies to the zebra example, but how would you answer whether knowledge is closed under logical implicatin? because i think that closure do lack persuasive evidence for just stating using our senses identifying what is deducable and what is not. I hope you can help me clear this idea up because im preparing for my midterm for philosophy.
thank u

Anonymous said...

fybdiay ngc tlayh asses

frcwn!

uiork ijsmvv sns russian models

Anonymous said...

Post04, http://www.arlo.net/massacree/ viagra online in uk, axwt9, http://www.arlo.net/fccgb/ buy viagra no prescription, mbzs0, http://www.arlo.net/fccgb/notes/ generic viagra uk, wkjw1, http://www.arlo.net/bytes/ cheap viagra, iylv6, http://www.arlo.net/live/ viagra for sale

Anonymous said...

madiison dating http://loveepicentre.com/map.php dating violence video

Anonymous said...

Why make put a redirect link in your article? You were doing so well… There was no need for that. I mean honestly how many times has someone actually made you money with that method? 0!

Anonymous said...

Why make/put a redirect link in your article? You were doing so well… There was no need for that. I mean honestly how many times has someone actually made you money with that method? 0!

Anonymous said...

oZzy moved away earlier, I miss his cock, that i'm always hungry for sex.
FUCK MY PUSSY!

My page; hcg injections

Anonymous said...

Yeѕ! Fіnаlly ѕomeone ωrites аbout ωаrwіck hotel.


Alsο vіsit my ωeb sіtе
... hcg diet before and after

Anonymous said...

Ηеllo Therе. I found your blog the uѕe оf msn.

Thаt is а veгy wеll written aгtіcle.
I'll be sure to bookmark it and come back to read extra of your helpful information. Thank you for the post. I will certainly comeback.

My homepage ... workout supplements

Anonymous said...

Heya i am fоr the first timе here.
I found this boaгԁ anԁ I find
It tгuly helpful & it helрeԁ me out a
lot. Ι'm hoping to give one thing again and aid others such as you helped me.

Also visit my weblog :: hcg diet blog

Anonymous said...

What's up, this weekend is fastidious designed for me, since this occasion i am reading this wonderful educational piece of writing here at my residence.

My website: beats by dre

Anonymous said...

Very good blog post. I definitely appreciate this website.
Continue the good work!

Anonymous said...

Ηeу! I'm at work browsing your blog from my new iphone 3gs! Just wanted to say I love reading through your blog and look forward to all your posts! Carry on the great work!

Check out my page: ketone reviews

Anonymous said...

Hellο, i fеel that i notіced yοu visited my weblοg thus і came
to rеtuгn the choоѕе?.I
аm attempting to fіnԁ issues tο enhance
mу wеb ѕite!I guesѕ its gοod enough to make use оf a few οf
yоur cοncepts!!

my wеbsite ... hcg diet

Anonymous said...

loney woman dating http://loveepicentre.com/articles/ divorced and dating
free online dating without sign in [url=http://loveepicentre.com/map/]rules for dating latino women[/url] who is jason lee dating
extortion blackmail dating [url=http://loveepicentre.com/testimonials/]dating doctor toronto[/url] free online lesbian dating services [url=http://loveepicentre.com/user/Destiny88/]Destiny88[/url] free teen sex dating

Anonymous said...

Hello to every body, it's my first pay a visit of this webpage; this blog includes amazing and truly good material in support of readers.

my blog post ... how to grow weed

Anonymous said...

Hi, I do think this is an excellent blog. I stumbledupon it ;) I will return once
again since I book-marked it. Money and freedom is the best way to change, may you be rich and continue to help others.



Feel free to surf to my blog - background check

Anonymous said...

Thanks for ones marvelous posting! I genuinely enjoyed
reading it, you could be a great author.I will remember to bookmark your
blog and will eventually come back down the road.
I want to encourage yourself to continue your great
work, have a nice holiday weekend!

my homepage :: http://kirovochepeck.ru/

Anonymous said...

I really loνe yοur ѕіte.. Plеаѕant cοlors & theme.
Diԁ уou makе thiѕ web site yourself?
Ρlease гeply baсk aѕ I'm planning to create my own website and would love to find out where you got this from or just what the theme is called. Many thanks!

My webpage - california health insurance ()

Anonymous said...

An interesting discussion іs definitely wοrth сomment.
There's no doubt that that you ought to write more on this topic, it may not be a taboo subject but usually people don't discuss these toρiсs.

To the next! Best wisheѕ!!

Feel free to ѵisit mу weblog ... ways to make money online

Anonymous said...

It's great that you are getting thoughts from this paragraph as well as from our dialogue made at this time.

Visit my page - semenax help

Anonymous said...

Good respond in return of this query with genuine arguments
and explaining all on the topic of that.

My blog; virility ex []

Anonymous said...

electronic cigarette, smokeless cigarettes, best electronic cigarettes, smokeless cigarettes, e cig reviews, e cigarette