Earlier I was telling Amy what a horrible movie Avatar is. She was shocked that I had seen it. I hadn't.
Why would I have to see it to know how horrible it is. Just like The Passion of Christ, can't you just tell? If you can't tell that, what can you tell?
It seems to me that we can know without seeing a movie that it's horrible. You think that, too. Maybe I'm picking the wrong examples, but it doesn't matter. Top Gun. The Matrix. Battlefield Earth. You knew they'd be bad. You didn't need to know via some inductive inference that rests on the premise that all observed movies hitherto have been bad. You knew from the trailers and the commercials. With Avatar it took just one look.
I mention this not to trash Avatar. To be perfectly fair, I haven't seen it. I mention this because I think there's an interesting argument by analogy here to consider:
(1) We can know that a movie will be horrible from the trailer even if there's some logically possible movie with just that trailer that is good (and, we don't need to make crazy modifications to that movie to make it good. We don't need to put the clips from the trailer into a trailer that the characters watch and mock in the movie.)
(2) Judging that a movie is bad without knowing all its parts is like judging that something shouldn't have happened without knowing all its parts.
(C) We can know that some state of affairs shouldn't have happened if someone could have done something to stop it without knowing all the facts and all the morally relevant features even if there's some logically possible larger state of affairs that includes it as a part that would be acceptable.
I've been thinking about moral epistemology a bit. Ross seemed to have the view that when we think about some state of affairs we can see that certain features of it count in favor or against various courses of action, but I don't think he thought we could arrive at a verdictive moral judgment without reasoning or inference. I think it's an interesting question as to whether we can know that certain verdictive judgments are correct without first establishing some premises about contributory reasons that are then treated as the basis for further deliberation. I cannot think of any reason to think that we cannot know that some verdictive judgments are true without reasoning from premises about contributory reasons, but others might. They have the epistemology of bad movies to contend with. We know some movies are just the sorts of things that shouldn't have been made and we don't need to reason from stills of silly, earnest blue aliens to figure that out.