Logic Test

[wynddancer]

I took the logic test. I got 14/15. I missed #15--I was kinda undecided about the answer and when I answered it I kinda knew I got it wrong and why the correct answer may be logical and valid but as the answer explains it's controversial in its correctness. Something may be discovered at a later date like that but I seriously doubt it--I'm a scientist at heart--I have a BS in biology, minor in chemistry. I have trouble buying the correct answer.

Here is there explanation: Answer 15. a) Water is a molecule composed of two hydrogen atoms and one oxygen atom. b) Every observation or examination by microscope has confirmed this.

 Invalid. Invalid but controversial in philosophical circles. If one defines water as a property that contains two atoms of hydrogen and one atom of oxygen only, then the argument above is valid. However, it is possible also that there may exist a substance that looks like water, boils as water, freezes as water, nourishes plants and life as water, and yet has a different chemical composition to what we know as water. There is nothing that could logically prevent this possibility occurring so the argument then becomes invalid.