This shows me all of you have studied MATH. You just don't know the difference. You should be able to tell a tree by its fruit. Do any of you even know there is a branch literally called MATHEMATICAL LOGIC? This is what you refer to. You ought to be using the FULL NAME of the logic you refer to as LOGIC. For thousands of years prior to Mathematical logic people KNEW logic as deductive logic. Inductive logic is another name for science. Now mathematical logic is popular people don't care about distinctions anymore.
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Does logic equal truth?
- Thread starter God lover
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raw_thought
Well-Known Member
I think you are confused because you think that I am saying that logic is not a tool to find the truth.
I am saying that in a 3 part syllogism if proposition 1 is true and proposition 2 is true and we know that the argument is valid then 3 has to be true.
I am saying that in a 3 part syllogism if proposition 1 is true and proposition 2 is true and we know that the argument is valid then 3 has to be true.
raw_thought
Well-Known Member
please no name calling. Please respond to my point about modus tollens ,which is logic (not only mathematical ) and has no truth statements. A therefore B is not a truth statement .It can only be a true or false statement if it refers to actual objects such as dogs and mammals.
Google "logic".
Logic is about validity not truth. I learned that in my first year logic course.
Yeah because you were taught most likely by a Math professor or Computer Science Professor. Philosophers of epistemology or logic itself would not define it that way nor would Aristotle. What do you know about classical logic as Aristotle taught?
please no name calling. Please respond to my point about modus tollens ,which is logic (not only mathematical ) and has no truth statements. A therefore B is not a truth statement .It can only be a true or false statement if it refers to actual objects such as dogs and mammals.
You are speaking strictly of a form. Modus tollens is logic and NOT math. This was pointed out by Aristotle thousands of years prior to Mathematical Logic. The fact M.P is in Mathematical logic does not make the two subjects the same.
raw_thought
Well-Known Member
Actually I have a BA in philosophy .Trust me, they require logic at university .
I am surprised that you are uninformed about something so basic (that logic is about validity not truth)
I am surprised that you are uninformed about something so basic (that logic is about validity not truth)
raw_thought
Well-Known Member
Yes, modus Tollens is about logic not math.
It is also about validity,not truth.
It is also about validity,not truth.
raw_thought
Well-Known Member
please no name calling. Please respond to my point about modus tollens ,which is logic (not only mathematical ) and has no truth statements. A therefore B is not a truth statement .It can only be a true or false statement if it refers to actual objects such as dogs and mammals.
You know you learned from a Mathematician by the terms used such as AXIOM, the use of HYPOTHESIS and CONCLUSION in a conditional statement. The belief the Contraposition is always valid, and so on.You are speaking strictly of a form. Modus tollens is logic and NOT math. This was pointed out by Aristotle thousands of years prior to Mathematical Logic. The fact M.P. is in Mathematical logic does not make the two subjects the same.
Yes, modus Tollens is about logic not math.
It is also about validity,not truth.
Please state WHAT makes you think it [LOGIC] is not about truth?
As a matter of difference Philosophers such as Aristotle never said what you claim. For Aristotle truth was in the PREMISES. Ussually when Aristotle demonstrated fallacies are the times he used premises he KNEW were false. In Aristotelian logic there is an epistimological element, which indicates TRUTH.
Again I emphasize people like you GOT logic is about validity from MATH or some intellectually dishonest philosophers.
Just for good measure let me add this point is again emphasized by Aristolte in The Rhetoric where he describes how syllogisms ought to be used in "GOOD" Rhetoric. How would rhetoric work if there was no truth element in it? His rivals the Sophist used rhetoric any which way they could to win a debate. Aristotle calls them out on this. His way which he represented Philosophy vs the Sophist way.
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raw_thought
Well-Known Member
Yes! I am talking about form. Modus Tollens is about the form of the syllogism ! It is not about if Propositions 1 and 2 are true or false. It is about validity.In other words if the RELATIONSHIPS of the propositions are logical.
Are you actually claiming that modus tollens is not a principle of logic???
Are you actually claiming that modus tollens is not a principle of logic???
I think you are confused because you think that I am saying that logic is not a tool to find the truth.
I am saying that in a 3 part syllogism if proposition 1 is true and proposition 2 is true and we know that the argument is valid then 3 has to be true.
Even this is UNTRUE. The logical form has a lot to do with the TRUTH. Even if you have all true propositions this does NOT MEAN the argument is valid. Do you know about argument MODD and Figure?
raw_thought
Well-Known Member
Obviously ,you do not know the difference between validity and truth. Yes, in common speach people use the terms interchangeably .However ,I am talking about the academic definitions that EVERY philosopher (including Aristotle ) agrees with.
Yes! I am talking about form. Modus Tollens is about the form of the syllogism ! It is not about if Propositions 1 and 2 are true or false. It is about validity.In other words if the RELATIONSHIPS of the propositions are logical.
Are you actually claiming that modus tollens is not a principle of logic???
Can you please explain why you think logic is not about truth?
I know about validity and I know only practical people care about it. I know of no philosophers in the 30's, 40's or 50's that cared about validity. What philosophers DID care about is SOUNDNESS. Other disciplines care about validity because the intent is different.
raw_thought
Well-Known Member
You kep giving me arguments that destroy your position!
Of course a syllogism with all true Propositions may not be valid.
That is because truth is not the same as validity!
I even gave an example of a true argument that is not valid.
Scroll back!
1.Nixon was president
2. Eisenhower was president
3. Therefore Carter was president
is an example of atruebutinvalidtrgument.
Of course a syllogism with all true Propositions may not be valid.
That is because truth is not the same as validity!
I even gave an example of a true argument that is not valid.
Scroll back!
1.Nixon was president
2. Eisenhower was president
3. Therefore Carter was president
is an example of atruebutinvalidtrgument.
raw_thought
Well-Known Member
You know of no philosophers that cared about validity???? So no philosopher believed in modus tollens????
raw_thought
Well-Known Member
No philosopher uses modus tollens????
raw_thought
Well-Known Member
1. All Martians eat snakes
2. Bob is a Martian
3. Therefore Bob eats snakes.
That is a VALID argument that is not true.
PLEASE take a basic logic course!!!!
2. Bob is a Martian
3. Therefore Bob eats snakes.
That is a VALID argument that is not true.
PLEASE take a basic logic course!!!!
You kep giving me arguments that destroy your position!
Of course a syllogism with all true Propositions may not be valid.
That is because truth is not the same as validity!
I even gave an example of a true argument that is not valid.
Scroll back!
1.Nixon was president
2. Eisenhower was president
3. Therefore Carter was president
is an example of atruebutinvalidtrgument.
You are confused. You gave an example of an invalid argument that boke so any rules that it is hard to that logic.
Use the proper rules and give me an example of all true premises and a true conclusion that is invalid. In your example Carter is not even in the premises.
I know truth and validity are distinct. I never confused the two. My point is the notion that logic is about validity did not spread through Philosophy but something else: namely Math, Rhetoric and Computer Science.
raw_thought
Well-Known Member
I think you are confused because you think that I am saying that logic is not a tool to find the truth.
I am saying that in a 3 part syllogism if proposition 1 is true and proposition 2 is true and we know that the argument is valid then 3 has to be true.