Consider the following sentence:
(1) I don't know that John kissed Mary.
When I assert this sentence, am I contradicting myself? The reason is as follows: following Stalnaker's view on the factivity of know, by asserting (1), I presuppose that the embedded sentence "John kissed Mary" is true. In other words, in asserting (1), I am in fact undertaking a prior commitment to the fact that John kissed Mary, namely:
(2) (It's a fact that) John kissed Mary.
But if that is the case, how the assertion of (1) is possible? If (1) is possible, then by conjoining (2) and (1), a Moorean sentence arises:
(3) %John kissed Mary, but I don't know that.
However, (3) is trivially odd. This rules out the possibility of asserting (1). But clearly (1) can be asserted and in fact we can find many sentences of the form "I don't know that ..." in ordinary discourse.
Does anyone have idea about the problem presented by the above examples? Thanks in advance!