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Sigurd
Tuesday, October 7th, 2008, 05:36 PM
Alright. So I just sat in my first Formal Logic tutorial, and up popped a question which I have not been able to get out of my mind: "Is the soundness of an argument subjective?"

The definition of a sound argument is "an valid argument, where the premises and the conclusion are true."

For the beginner: A valid argument is an argument where all premises are true, and it is impossible that the conclusion reached is false. e.g. "John Doe is a boy. All boys have XY chromosomes. Thus, John Doe has XY chromosomes."

On the other hand, an invalid argument is where the premises may well be true, and for all we know, the conclusion may also be true, but it is possible that the conclusion reached is false. e.g. "Hitler was a vegetarian. Hitler was evil. Thus all vegetarians are evil."

Premises and conclusion can all be true, but the argument may thus still be invalid: "I must be in Scotland, because the sky is blue and the grass is green." All threw are correct, but neither from the colour of the sky nor the colour of the grass does it follow that I am in Scotland (even though this is true) - I could well be in England, Zimbabwe or Argentina.

Enough of introductory stuff now. Let's use examples to highlight the point I am trying to make:

A sound argument which is irrefutable is: "It is midnight. At midnight it is always dark. Thus, it is dark now." That is a fact, which cannot be disproven.

On the other hand, an argument may well be sound in the conception of most, including the dictionary, but the truth that is contained in the premises may well be objective due to differing interpretations possible.

Let us assume for the ease of it that the sole dictionary definition of "murderer" would be "an evil person". (It is not, but let us just accept that).

Then the argument is put forth. "John Doe was a murderer. A murderer is an evil person. Thus, John Doe is an evil person."

That argument is technically sound. As far as most people on this planet are concerned, and as far as the dictionary we consulted is concerned, a murderer is an evil person.

Now, what if somebody felt that a murderer is not an evil person? As such, for that person, the argument would not be sound, because even though John Doe is an evil person, for that person for whom a murderer is not an evil person, one of the premises is false, and the argument can thus not be sound to the mind of that person.

Or let us use a different, easier-to-grasp example. What if an argument was to be - "Many Jews died in the Holocaust. The Holocaust was a genocide. Thus, many Jews died in a genocide." ... these are matters accepted as the truth by most people alive - but he who is a historical revisionist might beg to disagree.

Alternatively, a person might lack knowledge of the truth, two sides may take a different view of the truth, and it is indeed a matter unexplainable, thus they may believe concurrently that any logical argument based upon that supposed truth is true ... even if the other side will see it false

Or in short, does it matter if some people feel that a premise, or a conclusion is false - as long as it is generally agreed to be true? Also, is the truth of a matter were the truth is indiscernable and thus subject to one's interpretation subjective, and there can thus be no sound argument?

If the question asked is hard to understand, I'll try to rephrase it. ;)

Jäger
Tuesday, October 7th, 2008, 06:14 PM
For the beginner: A valid argument is an argument where all premises are true, and it is impossible that the conclusion reached is false.
Eh no, a valid argument doesn't need to have a true premise, the logic from premise to conclusion has to be correct to make an argument valid.
The truth of the premise is something unrelated, thus an argument can be false (as in not true) but still be valid.


On the other hand, an invalid argument is where the premises may well be true, and for all we know, the conclusion may also be true, but it is possible that the conclusion reached is false.
Simpler put, where the logic fallacies were used to reach the conclusion, of course by chance the conclusion can still be true.


Let us assume for the ease of it that the sole dictionary definition of "murderer" would be "an evil person". (It is not, but let us just accept that).

Then the argument is put forth. "John Doe was a murderer. A murderer is an evil person. Thus, John Doe is an evil person."

That argument is technically sound. As far as most people on this planet are concerned, and as far as the dictionary we consulted is concerned, a murderer is an evil person.
If you have just started a course on logic, then your final conclusion there will be that you always have to attack the premise in a valid argument.
As I explained before, a valid argument is no necessarily true, because it can have a false premise.


As such, for that person, the argument would not be sound, because even though John Doe is an evil person, for that person for whom a murderer is not an evil person, one of the premises is false, and the argument can thus not be sound to the mind of that person.
[...]
Or in short, does it matter if some people feel that a premise, or a conclusion is false - as long as it is generally agreed to be true?
That's why discussions (search for truth) work hierarchically, if the person is not an idiot he must accept the validity of the argument and simply state, with a new argument, that not all murderers are evil.
The problem of "subjective" truth arises, when we reach a premise we agree on, but which isn't true, but this is actually not a question of subjectivity, but simply a problem of too little knowledge, simply someone was missing who told us the missing information to declare the premise false.
Thus it is not a question of subjectivity, but it is the realization that we shall not think we will ever reach 100% truth, however if we can use our conclusions to predict situations quite accurately, then we can assume we are very close to the truth, to the objective truth.
Because if every truth has to proof itself in predictions (independent of the subject), it is objective.


Also, is the truth of a matter were the truth is indiscernable and thus subject to ones interpretation subjective, and there can thus be no sound argument?
No, in such cases we simply don't know whether it is true or not, so we simply don't have a truth, just assumptions, and only idiots will sell it as truth (like with relativity from Einstein and in general Jewish physics).

Moody
Thursday, October 9th, 2008, 08:15 AM
Or let us use a different, easier-to-grasp example. What if an argument was to be - "Many Jews died in the Holocaust. The Holocaust was a genocide. Thus, many Jews died in a genocide." ... these are matters accepted as the truth by most people alive - but he who is a historical revisionist might beg to disagree.

Alternatively, a person might lack knowledge of the truth, two sides may take a different view of the truth, and it is indeed a matter unexplainable, thus they may believe concurrently that any logical argument based upon that supposed truth is true ... even if the other side will see it false

Or in short, does it matter if some people feel that a premise, or a conclusion is false - as long as it is generally agreed to be true? Also, is the truth of a matter were the truth is indiscernable and thus subject to one's interpretation subjective, and there can thus be no sound argument?


This reminds me of the general criticism of syllogistic logic; - it is based on tautologies, and derives from a game of definitions.
of course, a perfect syllogism can be false, just as a bad syllogism can be true.

But is the agreement of defintions only merely true?
Isn't this rather circular and lacking the necessary detachment for "objective truth"?

Likewise, can there be any truth which is not filtered through the human subject?

Are there nonhuman truths, for example?

Dr_Jan
Friday, April 16th, 2010, 08:21 AM
The point of logic isn't to tell us what's true. The point of logic is to help us discern what we may conclude from what we know. Logic is about how to proceed from what we accept as true to something new.

A valid argument is one in which, IF the premises were true, the conclusion would have to be true.

Validity is a matter of the FORM of argument. It has nothing to do with whether the premises are actually true. But a valid form of argument means that, if you believe the premises are true, you would have to accept the conclusion.

John Doe was a murderer.
A murderer is an evil person.
Thus, John Doe is an evil person.

This argument is valid. That is, IF you accept the premises as true, you would have to accept the conclusion.

You can tell me you think some murderers aren't evil, but that doesn't hurt the logic of the argument - it doesn't attack the reasoning. It only tells me you don't agree with one of the premises.

Take a look at the reasoning in your old geometry text book. The logic, the reasoning, takes us from things we already have established as true, to new things.

Separate the logic, and the process of reasoning things out, from the question of what is true. They're two completely different things.