Logic, the prerequisite of all truth

[Aetherous]

8)

 

Like I said, I don't agree. I still think Logic is the prerequisite of all truth. I think it defines truth. Not personally interested in discussing it further (although, go ahead)...but I am interested to see if the course changes my mind after a year.

[Astral Monk]

Like I said, I don't agree. I still think Logic is the prerequisite of all truth. I think it defines truth. Not personally interested in discussing it further (although, go ahead)...but I am interested to see if the course changes my mind after a year.

lol, the end!

 

any good basic logic course will tell you truth is not covered by logic--that is, truth values are assumed but not discovered or assessed (other than by testing formal deductive structure which is not additive to knowledge). Classical logic looks at validity only. Semantic logic is truth preserving.

 

Lets continue next year. Maybe I'll even dust off my logic text shelf lol.

 

8)

[Eques Peregrinus]

Let's restart the discussion more formally. First by defining the booleans values and their operators, which we are going to use as axioms.
 
Let B = {true, false}
 
Let ¬ the negation on one element a in B, such that:

 a | ¬a
---+----
 f |  t
 t |  f

 
Let ∧ the conjunction on two elements a, b in B, such that:

 a | b | a∧b
---+---+-----
 f | f |  f
 f | t |  f
 t | f |  f
 t | t |  t

 
Let ∨ the disjunction on two elements a, b in B, such that:

 a | b | a∨b
---+---+-----
 f | f |  f
 f | t |  t
 t | f |  t
 t | t |  t

From them we can define others operators, which are more traditionally used.
 
Let → the implication, such that:

 a | b | a→b
---+---+-----
 f | f |  t
 f | t |  t
 t | f |  f
 t | t |  t

To illustrate why it is defined as such, lets use an example with a common card game. With such a card game, the following tautology H can formulated: "if a card is a heart, then it is red". Then let's observe the following cases:

• The card is a heart and it is red: Then H holds.
• The card is not a heart and it is red: Then H still holds, the card can be a diamond.
• The card is not a heart and it is not red: Then H still holds, the card can be a club or a spade.

If the card game is a common one, only these 3 cases can occure. If this fourth case occures:

• The card is a heart and it is not red: Then H does not holds, the card game is not a common one.

We can also observe that if "a" is false, then "a→b" is true regardless of "b", more commonly said "we can learn nothing from a lie" or "we can learn nothing from something false".
 
This possibility to formalise implication as such is particularly interesting, because it is possible to express it with 2 of our initial operators. "a→b" is equivalent to "¬a∨b".
 
Other useful operators are the reverse implication and the equivalence.
 
Let ← the reverse implication, such that:

 a | b | a←b
---+---+-----
 f | f |  t
 f | t |  f
 t | f |  t
 t | t |  t

 
Let ↔ the equivalence, such that:

 a | b | a↔b
---+---+-----
 f | f |  t
 f | t |  f
 t | f |  f
 t | t |  t

 
Remain to define the quantifiers, used to "speak about" elements in a set S verifying a property p.
 
Let ∀ the universal quantifier. If all elements of S verify p, we write "∀e in S, p"
 
Let ∃ the existancial quantifier. If one element of S verify p, we write "∃e in S, p"

For historical reasons, logical reasonnings are often made using rules of inference (modus ponens, modus tollens, sillogisms, etc...) often written following the format:
 
premise #1
premise #2
...
premise #n
__________
∴ conclusion
 
which can be rewritten as:
 
(premise #1 ∧ premise #2 ∧ ... ∧ premise #n) → conclusion

[Aetherous]

I'm starting a new thread for the exploration of this specific course, with owner permissions.

Feel free to continue this thread however you guys wish.

[Wu Ming Jen]

It may be logical to say that the sun rises every morning but it's not true because we are all spinning.

 

It's all prospective or current situation that creates the logic but it is changing, so truth changes with it, false becomes true, true become false and we are all spinning did I mention that?

[Eques Peregrinus]

Well, what is Truth can provoke a very deep philosophical debate. So deep, in fact (as more or less implicitely stated in my previous post), that the properties true/false, as used in logic, are taken as an axiom, without much reflection. And quite paradoxally, this axiom needs itself to be considered true. (Hell! What a minefield!)

 

Now, a crucial point that did not appears in this thread is the difference between "critical thinking" or "rationality", and "logic", which are two different things. In their relations, rationality uses logic, but in certain cases uses also intuition and sometimes emotions to reach conclusions.

 

This is the implications of emotions in that decision process which is subject to much criticism by philosophers, because these emotions are changing depending on the mood of the individual making the reflexion. This is why the course (about which this thread began) put so much emphasis on fallacies and cognitives biases.

 

To illustrate the difference between rationality and logic:

Suppose that you hear your door bell ringing at 8:00 in the morning. You can make many hypothesis about what it is about.

• The postman came and has a recommended letter you had to sign.
• The postman came hand has a large package he do not want to let in front of the door.
• The neighboor has something to tell us.
• Children are making a joke.
• The doorbell is broken.
• Jehovah witnesses.
• Aliens!
• ...

Among this unlimited number of assumptions, the manner in which we will react is not logical, because all these possibilities are logical, even if certains of these events are (very) unlikely. Choosing to open the door while smiling instead of kicking the door while pointing a rifle (at the potential Jeh... aliens) is a rational choice depending on our experience/intuition/mood/etc...

[Wu Ming Jen]

Logic is an abstraction made from abstractions. Love it. I prefer common sense where you need no knowledge but can take the best course of action spontaneously. 

[Papayapple]

I'm always wondering why do some people find such abstract studies amusing.
Sure it's probly good science, but what can a normal person get from all this? Apart from good tools to win an argument?

Yesterday I had a conversation with a buddy about music, and I say something about objective listening.
And heeey he goes talking about how objectivity doesn't exist and "woa dude nothin's real! checkout Kant!" 

And I just lost interest.

What's the deal really?

Confused Papple.

[Papayapple]

Logic is an abstraction made from abstractions. Love it. I prefer common sense where you need no knowledge but can take the best course of action spontaneously. 

Was just about to add that.

is there any logic in synchronisity actually?

[Papayapple]

Well, for me, it's kind of like when someone calls you by the wrong name. Let's say that your name is Bob and someone calls you Steve. It's easy enough to shrug off. At the same time, it's not actually your name. That sort of tweak and the preference for smoothing things are not really fitting is what brought me into abstract things.

Can you please expand on what you said? Where exactly is the link?

[thelerner]

Food for thought.

 

Truthfulness.. Daeluin posted this in another thread- (from tl Thomas Cleary, from Taoist Classics Volume 4, I Ching Mandalas, Arcana-- Lo Writing (Lo Shu)

 

When truthfulness is based on kindness, forming the final link in the circle, you are steadfast and unwavering; true will appears, and wandering attention quiets down. Celestial and mundane intentions combine, so that you can be joyful, angry, sad, or pleased, all without selfish desire.

 

 

Here's the longer quote-

Truthfulness, Liu continues, has the meaning of true belief: "Truly believe in kindness, and you can be kind. Truly believe in justice, and you can be just. Truly believe in courtesy, and you can be courteous. Truly believe in wisdom, and you can be wise. Truthfulness alone can be kindness, justice, courtesy, and wisdom, all according to the changes that take place in the mind."

 

Pursuing the definition of truthfulness to a deeper level, Liu calls it the means to restore the primal and equates the experience of the return of the primal with truth. For a practical expression of truthfulness as a means, Liu turns to a section of the Taoist classic Tao-te Ching traditionally used as a meditation guide: "In a flash of enlightenment, something is there. In the utter darkness, vitality is there. That vitality is very real, at its center is a truth." This truth, Liu says, is the experience of the return of the primal, attained through profound abstraction.

 

Liu also uses the scheme of the five virtues to elaborate on the outgrowth of this return to truth, or restoration of the primal. When wisdom is based on truthfulness, he says, knowledge is not used randomly; you are free from greed and ambition, your mind is peaceful and its energy is harmonious. Then you are pleased with reality and produce courtesy from within wisdom. When courtesy is based on wisdom, you can harmonize with those unlike yourself and you do not do anything discourteous; impatience sublimates, so that you no longer become angry but instead become just.

 

When justice is based on courtesy, Liu continues, you are just without bias, able to adapt to changes while following guidelines in your actions. Then you delight in good and develop kindness. When kindness is based on justice, you are kind without being weak, as good as possible, without evil, sincerely whole-hearted, without duplicity. Then you are free from selfish desires and are therefore truthful.

 

When truthfulness is based on kindness, forming the final link in the circle, you are steadfast and unwavering; true will appears, and wandering attention quiets down. Celestial and mundane intentions combine, so that you can be joyful, angry, sad, or pleased, all without selfish desire.