If any belief of yours may be mistaken, how can you say without qualification that you "do know many things"? It would be a contradiction to say: "Quito is the capital of Ecuador, but it is epistemically possible that it is not".

If a doctor, after running numerous tests, told you you had cancer, and you told your family, "I am sick, I have cancer", would you feel you had qualification for telling them so? Would the possibility that your doctor was wrong, be reason to tell your family not to worry?

Justifications can't make a false belief true, but justifications, for any rational man, are the reasons why we believe something to be true.

--

You frantically run through the city of Quito, screaming, "What is the name of this city?!". Most people, seeing how insane you appear, attempt to reassure you, "The name is Quito, sir, the city's name is Quito!". You encounter sign after embroidered sign with the name "Quito" in Spanish positioned under many of the open shops, and in your stride you even pass the Cathedral of Quito. You want to believe, you really do, but you know you might be mistaken - you know everyone in the city might be wrong! Finally you approach city hall, located in the central district, and think, "This will be my proof!". You enter city hall, gasping for air, and approach the closest desk which appears to offer information. "What's the name of this city?!", you shout. The man looks at you bewildered, and points to the brochure to his left, which, in bold-face, spells out "Quito". You begin to feel a sense of euphoria, relieved, you thank the man, exit the city hall, and then approach a nearby cafe for some local pallela. Once seated, you begin waiting for your lunch, hands behind your neck in a relaxed pose.

All of a sudden you cringe and lose breathe for a moment, your face gets pale. A thought races through your mind: "Wait, what if the brochure was wrong?!?!". You jump up with a seemingly vengeful force, running towards city hall screaming, "Get Augusto Barrera Guarderas on the phone!".

Why were you in doubt whether the city was Quito in the first place?

Because the person doubts every contingent truth that is claimed, that's why!

And his reason for that is? My point is that doubting cannot take place in a vacuum. We need a positive reason (Peirce) to doubt.

What is a positive reason? And are there negative reasons too?

Take the statement that Quito is the capital of Ecuador. Negative reason. It might be false. Positive reason: The Ecuadorean legislature went into secret session, and there is evidence that there is heavy sentiment for changing the capital to Guyaquill.

I think he just means that we cannot doubt without a reason of some sort. I thought I could doubt without a reason, but then again, maybe sometimes I have a reason when I doubt but don't know what the reason is.

It is epistemically possible that Quito is the not the capital of Ecuador, since my evidence that it is is inductive and not deductive. So it does not follow necessarily from its evidence. (Of course, there is another sense of "epistemically possible". ~P is epistemically possible= for all I know, P is false. In that sense, to say I know that P, but ~P is epistemically possible would be a contradiction). The negations or all contingent propositions are also epistemically possible in the sense that they are supported non-deductively.

So the following would be a contradiction:

"I know that P, but for all I know, P may be false."

Is the following also a contradiction?

"I know a million things, but for all I know, at least one of them may be false."

The latter statement seems to be true, since there is a non-negligible epistemic possibility that somewhere among the many things we claim to know with total confidence are a few that are actually false.

I think there's always a reason why we doubt, just as there's always a reason why we believe. Whether or not the reason is bad or good is a different story. I also think you're right in that we may not know the reason why we doubt or why we believe.

But I am talking about a reason, not a cause. I mean a justification for doubting. What kind of justification can you have if you don't know what the justification is? There is always a cause or explanation for doubting, just as there is one for every event. But it is justification, not cause, I am talking about, although a justification may also be a cause. The point is to show that doubting in this case is justified. Of course, it has a cause. Otherwise you would not doubt.

So the following would be a contradiction:

"I know that P, but for all I know, P may be false."

Is the following also a contradiction?

"I know a million things, but for all I know, at least one of them may be false."

The latter statement seems to be true, since there is a non-negligible epistemic possibility that somewhere among the many things we claim to know with total confidence are a few that are actually false.

That's not a contradiction.

I do not agree with what you have written; however, if you switch "may" with "might," then I would agree with what you have written. It still wouldn't be a contradiction, but it's perfectly fine to say, "I know that P, but for all I know, P might be false." I would not say, "may," for that implies a good reason for thinking it's false, and if that's the case, then you shouldn't be saying you know P.

"I am in Florida" and "I am in South Carolina" is not an example of a contradiction. "I am in Florida" and "I am not in Florida" is an example of a contradiction.

Both are contradictions, and I would, as Z. says, understand someone who uttered them as saying, "I think I know" rather than, "I know".

What you said at the end is not fair. You switched from knowing to "claiming to know". With that change I would agree with you. You cannot know what is false, but you can certainly claim to know what is false. But isn't is obvious that claiming to know and knowing are two very different things?

How likely is it that everything we confidently believe to be true (and therefore claim to know) is actually true? Given the vast number of things we claim to know, it does not seem very likely. Now and again, things we believe beyond reasonable doubt turn out to be false. It is reasonable to think, therefore, that not all our confident beliefs are true. In other words, it is probable that we do not know all we claim to know. Each individual confident belief is almost certainly true, but their conjunction is probably false.

Does this matter? Should we always interpret "I know", when applied to contingent propositions, as meaning "I think I know"?

I just rarely feel confident saying I know, since I do not know that I know.

The British philosopher, Harry Prichard, was known for never saying he knew and saying, instead, "I strongly believe", just as he would never say, "I promise (to do so-and-so)" and saying instead, "I fully intend (to do so-and-so". And for the same reason. He did not think he could be certain that he knew, and he did not think he could be certain that he would perform his promise. But, of course, it made no difference, since people would just translate, "I strongly believe" into "I know", and "I fully intend" into, "I promise", and indulge Prichard in his little curlicues.

How likely is it that everything we confidently believe to be true (and therefore claim to know) is actually true? Given the vast number of things we claim to know, it does not seem very likely. Now and again, things we believe beyond reasonable doubt turn out to be false. It is reasonable to think, therefore, that not all our confident beliefs are true. In other words, it is probable that we do not know all we claim to know. Each individual confident belief is almost certainly true, but their conjunction is probably false.

Does this matter? Should we always interpret "I know", when applied to contingent propositions, as meaning "I think I know"?

ACB,

I brought this up in another thread actually. It's really about your own personal comfortability.

See: http://www.philosophyforum.com/philosophy-forums/branches-philosophy/epistemology/6814-sufficient-conditions-knowledge-9.html

Starting on page 9, I think. I reiterate what you say here.

Excerpt:

ACB,
I brought this up in another thread actually. It's really about your own personal comfortability.

While the above is true, it is still false that for all you know, some of the things you know may be false. What is true is that for all you know, some of the things you think you know are false and thus you don't know them at all.