Deductive logic test

[Sblast]

I scored 15 (100%) on the first test. I gambled was testing with regard to rigor instead of just messing around with trick questions [meaning suppressed premises are a fair game]. Apparently I gambled correctly.
I scored 15 (100%) on the second test. Replacing the order of premises in 13, I didn't have to construct a single truth table through out the tests.

What's exactly the point in posting this to people who didn't study formal logic? It's fun, tho logic isn't intuitive and the tests are not exactly the hardest after a short course/introduction .

"a) Whatever goes up must go down.
b) The train robbers are up before the beak.
Conclusion
Therefore the train robbers will be sure to go down."

Here's one for you:

The moon is made out of cheese and isn't made out of cheese.
All cheese is Roquefort cheese.
The moon is made out of cheese.
Therefor, Roquefort cheese is moon cheese.

[Herr Abubu]

15/15 on both.

[Mortimer]

Here's one for you:

The moon is made out of cheese and isn't made out of cheese.
All cheese is Roquefort cheese.
The moon is made out of cheese.
Therefor, Roquefort cheese is moon cheese.

valid

[Herr Abubu]

Invalid. First premise contradicts itself, and premise 2 and 3 implies that moon cheese/the moon is Roquefort cheese, not the other way around.

[Mortimer]

Invalid. First premise is contradicts itself, and from 2 and 3 implies that moon cheese is Roquefort cheese, not the other way around.

yes thats true

[Mortimer]

but if moon cheese is roquefort cheese, isnt roquefort cheese mooncheese?

[Mortimer]

also that there is moon cheese is not fitting, it should be moon is made out of roquefort cheese because all cheese is roquefort cheese. that roquefort cheese is moon cheese makes no sense in this context

[Mortimer]

i think i got it now, roquefort cheese is moon cheese is valid as in the moon is made out of roquefort cheese the cheese in the moon is roquefort cheese.

[Sblast]

Invalid. First premise contradicts itself, and premise 2 and 3 implies that moon cheese/the moon is Roquefort cheese, not the other way around.

Given the first premise is a part of the argument, the argument is valid. An argument is valid iff it is not possible for the conclusion to be false if the premises are true. It's impossible for the premises to be true when a contradiction is a premise (since it's always false) - there's no possibility that the premises are true and conclusion false - hence, the argument is valid. It's known as the principle of explosion.

valid

[Herr Abubu]

Given the first premise is a part of the argument, the argument is valid. An argument is valid iff it is not possible for the conclusion to be false if the premises are true. It's impossible for the premises to be true when a contradiction is a premise (since it's always false) - there's no possibility that the premises are true and conclusion false - hence, the argument is valid. It's known as the principle of explosion.

So if I understood correctly, if the first premise is a contradiction -i.e., something is and it is not simultaneously - then anything goes, basically? Both are true, so you can conclude what follows from either is or is not? But isn't the conclusion still invalid since all chese is Roquefort cheese although all Roquefort cheese isn't moon cheese? And doesn't this go against the law of noncontradiction, that A cannot be both A and not A at the same time?