If the only financial institution in town is located on the only riverbed in town, is the sentence "Judy went to the bank" still ambiguous?

Nice try. But the answer is yes, it is still ambiguous. The river's bank is presumably much bigger than the financial bank, so "Judy went to the bank" could mean she is fishing on the river's bank outside the financial bank or she could be cashing a check inside the bank on the bank. Now, if you had said that the only river in town is located entirely within the financial institution and the only place to be in the bank is on the bank ...

Hi. Take the following syllogism : John believes that green people should be killed. Mushmush is a green person, a neighbour of John. ====================== Thus, John believes that Mushmush should be killed. Formally, the argument seems valid. However, in reality it doesn't work. A persona can believe that all people with quality X should be killed, but not think it about a specific person he knows. So is there a logical contradiction here? What happens? Thank you, Sam

The syllogism is still valid (i.e., if the two premises were true, the conclusion would have to be true). But you have just found a case (Mushmush) that falsifies the first premise. It turns out John does not really believe that all green people should be killed, but he believes (at least) one green person (Mushmush) should not be killed. Good for logic and good for Mushmush!

This is a nice case of what can go wrong when you (i.e., I) do philosophy too quickly! As Richard charitably suggests, (I think) I was reading the argument (too quickly) to say: 1. John believes that all green people should be killed, and 2. John believes that Mushmush is a green person, 3. Thus, John believes that Mushmush should be killed. Mitch is right that the original question left "John believes" out of premise 2, so it's clearly not formally valid: 1 could be true, but if John does not believe Mushmush is green (even though he is), then clearly 3 would not follow. With premise 2 written as here, with "John believes," then it looks much "closer to valid" but "valid" is not like horseshoes or hand grenades, so close does not count. It's hard to see how John could miss the inference, but perhaps he is like some racists in literature who sincerely hold universal derogatory beliefs about another race and sincerely reject that belief about their friend or neighbor who they...