Determine the validity of the argument> Martians are green. Roger is not green. Therefore Roger is not a Martian. I say this is valid. Is this correct?
I agree but get a third opinion.
Yes, your determination is correct. The argument you presented is valid.
To explain why it is valid, let's break down the argument:
1. Martians are green. (Premise)
2. Roger is not green. (Premise)
3. Therefore, Roger is not a Martian. (Conclusion)
The conclusion (Roger is not a Martian) logically follows from the premises (Martians are green and Roger is not green).
In this argument, the premises establish a general statement about Martians being green and a specific statement about Roger not being green. By combining these two premises, the conclusion is reached that Roger is not a Martian. This inference is valid because it conforms to the structure of a valid logical argument, known as modus tollens - if A implies B, and B is not true, then A must also not be true.