agrote wrote:No. I mean "Is justified true belief the same as knowledge?" Or, is the following true...
A knows that P if and only if
1. P is true
2. A believes that P
3. A's belief that P is justified (or has adequate evidence to support it, perhaps)
I am on record as having
already accepted this definition of "knowledge" (at least as a working definition), and, despite some reservations, I see no reason to discard it now.
To examine this definition, let's look at some beliefs that would not constitute "knowledge." Take, for example, a person's belief in the existence of unicorns. Although the person may sincerely believe in their existence, there would be no indicia of truth that would allow the person to assert that his belief was either "true" or "justified." Likewise, a belief that one is possessed by demons would lack the necessary elements of truth and justification.
On the other hand, let's suppose that a person believes that she is the queen of Portugal, and further let's suppose that she actually
is the queen of Portugal, but her belief is based upon messages that she has received from magic pixies. Now, her belief is true and it is a sincerely held belief, but, because her belief is not based upon the truth of the proposition (it is, instead, based upon a phantasm), it is not justified. In other words, although she believes something that is true, she can't be said to
know that she is the queen of Portugal. The fact that her belief actually coincides with the truth is, in this respect, merely that: a coincidence.
In contrast, my belief that I am currently typing this text on a computer that is in front of me satisfies all three conditions: (1) I sincerely affirm that proposition (in that I believe it to be true); (2) the proposition is "true" (in that it satisfies the criteria of "trueness"); and (3) my affirmation is based upon the truth of the proposition (or, in other words, it is "justified"). I can, therefore, affirm that I
know (insofar as it is possible to know anything) that I am currently typing this text on a computer in front of me.