rhutchin

No, I haven't. However, I would be willing to bet that logical arguments can be either true or false in the conclusions they draw. If that is true, then logical arguments are not necessarily sound arguments.

A logical argument would require true premises to reach a true conclusion. So, if an argument does not address all alternative explanations, then it is possible for one of its premises to be false because it opposes an alternate explanation.

So, what do you say? Can you have a logical argument that draws a conclusion that is false?

Doug Shaver

Absolutely. Logic is just an intellectual tool, and a logical argument would be an argument that uses that tool. Like any other tool, there are right ways and wrong ways to use it.

To a logician, an argument (in this context, "logical" is redundant) is any set of statements such that the person making them claims that one of the statements, called the conclusion, is demonstrated or proved by all the others.

There are two possible versions of this claim. One is that it is logically impossible for all the premises to be true while the conclusion is false. Such an argument is called deductive. The other is that it is unlikely that all the premises could be true while the conclusion was false. This would be an inductive argument.

A deductive argument is called valid if it actually is impossible, as a matter of logical fact, for the premises to all be true while the conclusion is false. In this case, to affirm the premises while denying the conclusion would be in effect to affirm a contradiction. If the premises of a valid argument actually are true, then the argument is said to be sound.

An inductive argument is called strong if it actually is unlikely, as a matter of logical fact, for the premises to all be true while the premise is false. In this case, to affirm the premises while denying the conclusion would be in effect to affirm what is probably a contradiction. If the premises of a strong argument actually are true, then the argument is said to be cogent.

If an argument is sound, then its conclusion is necessarily true. A sound argument is the only kind that guarantees a true conclusion.

I suspect you're using the word "logical" to mean "valid." The premises of a sound argument are true by definition, but otherwise no argument needs true premises to have a true conclusion. If any premise of an argument happens to be false, then the argument does not prove the conclusion, but failure to prove a conclusion does not itself make the conclusion false. Any true statement can be the conclusion of an infinite number of invalid or unsound arguments. (An invalid argument is unsound by definition, but if it is invalid, then the truth of its premises is irrelevant.)

I don't quite understand what you're trying to say here.

rhutchin

Let's use an example. We have a premise - Life originally arose through spontaneous generation from non-living matter. We then use that premise to build a logical argument to support the idea of common descent (evolution). An alternate explanation is that life arose supernaturally. If we ignore the alternative in the logical argument, then we can have a premise that is not necessarily true as we assume (i.e., we have a premise based on the presumption that it is true). Regardless, if an alternate explanation exists for any premise and the truth of the premise cannot be determined, then the soundness of the argument can be questioned. By not addressing all alternative explanations in our premises, we can end up using a false premise that then leads to a false conclusion (that we think is true).