Validity and Soundness

I'm unclear on your response.  I thought the point of identifying fallacies is to show that there's bad thinking in an argument, which I assume means it shows the argument is either unsound or invalid.  Am I misinterpreting what you're saying?

I was trying to get clarity on what the difference is between these concepts, at least as used on this website.  This would go to the question of whether a particular type of fallacy makes an argument invalid or makes it unsound.

I think this is what you seek. A valid argument may still have a false conclusion because the structure is valid, but one or more premises are in error. When we construct arguments, we aim to construct one that is not only valid, but sound. A sound argument is one that is not only valid, but begins with premises that are actually true. 

[To Darren]

I thought the point of identifying fallacies is to show that there's bad thinking in an argument, ...

This part is correct

which I assume means it shows the argument is either unsound or invalid. 

...or fallacious. Only a deductive argument can be unsound or invalid. Most arguments people deal with on a regular basis are inductive or abductive, and don't fit nicely into a syllogism that can be demonstrated to be in/valid or un/sound. Other "arguments" are implied and often just statements or claims, lacking the form of an argument. For example, "Bill is wrong because he's a poo poo face." There are no premises to evaluate so validity and soundness don't apply. But we can certainly spot the fallacy (ad hominem (abusive) ). We CAN attempt to make a formal deductive argument from virtually anything, but this often takes assumptions (but a good exercise especially when the arguer is present and participating in the exercise.) For example,

P1. If Bill is a poo poo face, then he is wrong.

P2. Bill is a poo poo face.

C. Therefore, he is wrong.

Here we have a valid argument because if P1 and P2 are true, then the conclusion MUST be true. However, it is not sound (at least one of the premises is false). We can say this argument is both fallacious and unsound, once we formalized it. Again, it is good practice to put into an argument form like this, but not always possible.

OK.

I was confused because of something you wrote a couple of days ago, where you said that an argument with an untrue premise can't be valid.  You were responding to an argument by Jacob (posted as "Sound Logic"), which I'm pretty sure was an inductive argument.  You responded:

"Guns can allow for more serious harm to be done," More serious than what? Without this, we cannot have a true premise, thus the argument can't be valid." 

This implies that an inductive argument is invalid when a premise is untrue.   But I view "invalidity" (as Dr. Richard wrote above) as referring to bad reasoning, not the truth of the premises, and only in deductive arguments as you pointed out.   That's what got me confused and needing clarity on the use of the terms  (perhaps you meant to say "fallacious", not "invalid").     Help!   Thanks.

It was a weak argument being used so I was referring to building a strong argument (deductive argument was being attempted). Remember that a valid argument means that IF both premises are true, then the conclusion must be true. My thought on this was if we can't know, then we can never say that the premise is true. Therefore, we can never know if the conclusion is true or not. Perhaps it would have been easier and less confusing (and controversial) just to say that if we cannot tell if the premise is true, they we cannot say the argument is sound.