# Humans and logic

Discussion in 'Human Science' started by arfa brane, Aug 17, 2015.

1. ### arfa branecall me arfValued Senior Member

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A few logical statements which are either true or false:

1. If something is logically true, it has always been true.
2. Humans are logical.
3. It has always been true that humans would be logical.

3. ### DaeconKiwi fruitValued Senior Member

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1. Doesn't follow. Can you elaborate?

2. No. Have you ever met a Human?

3. No. See #2.

5. ### arfa branecall me arfValued Senior Member

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Of course, there are statements about temporally true or false things, such as: "George Washington is the president of the United States". This is false today, but it can be generalised to "George Washington was the first president of the United States".

So what I'm saying is that this has always been true, it must be because we live in a universe that it's true in, so it must have been true that George Washington would always have this history.

To put it vacuously, it must be true that things which are true today would have (always had) a unit probability of being true.

Last edited: Aug 17, 2015

7. ### arfa branecall me arfValued Senior Member

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The second statement I support thusly:

Humans are logical because they build computers which are logical systems. Locally, these depend on things which are true having a probability of being false in the future--the logic is temporal or conditional on there being different times and variables being either true or false--indexed by this difference in time.

We, or our computers arrange these times in a sequence and this sequence means we can define pre- and post-conditions on abstract 'programs', and prove using logic that the programs are correct.

P.S. Because George Washington was the first president of the United States, he is the first president of the United States, and always was.

Last edited: Aug 17, 2015
8. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Humans CAN BE logical.
Somewhat different from humans ARE logical.

9. ### DaeconKiwi fruitValued Senior Member

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I'm not sure I fully follow your distinction between "logically" true and any other kind of true.

Do you refer to axioms or tautologies?

What about a situation where something isn't currently true, but will be true in the future. Or something that could potentially become true in the future?

Humans definitely can be logical, but it seems to be a rare trait, not a common one.

10. ### arfa branecall me arfValued Senior Member

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Well, we can only project a probability of a particular thing being true in the future. There are logically true things that don't depend on the existence of time, for instance that every prime number has only two divisors. I don't know that I'm right, but I imagine the number of logical truths which are independent of time is much larger than the number of historical events in the universe. I think this because in order for this universe to have the physical laws it does, they must have existed before the universe did, independently of time.

An historical truth is a thing that wasn't (temporally) true before the event, like say the Battle of Hastings, but it obviously was going to be because it became true, and it remains true today. The present includes all of the past, the future is a projection. All of the previous statements are logical--either true or false.

11. ### arfa branecall me arfValued Senior Member

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Not logically different.

12. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Really?
So in your world all water is ice?
Or maybe steam?
And all humans are dead? Asleep? Angry?

13. ### arfa branecall me arfValued Senior Member

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Water, ice and steam are all things that can be each other. They are all the same "stuff"--molecules.
Maybe one of them is.

14. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Agreed, but the point is: IS isn't the same as "can be".

15. ### arfa branecall me arfValued Senior Member

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All humans is humans, all humans isn't can be humans.

Thanks, I guess I just needed to think about it the right way.

Here I was, thinking that since humans can be logical and build logical machines, that humans are logical.

Laugh, I thought too that since Washington could be the first president of the US, that he was in fact the first president, which also means although the man is dead, he is still the first and the only first, which means not all humans can be the first president of the US.

But thanks for the correction.

Last edited: Aug 17, 2015
16. ### arfa branecall me arfValued Senior Member

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I think I can see what might have thrown some people.

A statement like: "George Washington is the first president of the US." looks like it has a temporal mistake. It should say, you think ". . . was the first president . . ."; you most likely think that there should be a date included--when is Washington the first president--the context is historical, etc. Maybe it's a statement from some timeline of American history, you think.

To keep the present tense, just add a couple more words: "George Washington is the first president of the US in history.". What changed? Is the last statement now logically correct because it looks temporally correct?

17. ### arfa branecall me arfValued Senior Member

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Logic:

Humans are logical because they can be logical.
Humans can be logical because they are logical.

Spot the difference. It has to do with temporality. If both statements are true, then "are" and "can be" are logically equivalent (and not temporally equivalent).

18. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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Water is ice because it can be ice.
Water can be ice because it is ice.
Makes it rather hard to drink, neh?
And, mutatis mutandis, the same for humans and asleep/ dead/ angry.

Humans being logical is a temporary conditional state. I.e. it's more accurate to say "humans are capable of behaving/ thinking/ acting logically".
If humans WERE logical then there'd be no illogical human acts/ statements. And we know for a fact that's not true.
I.e. neither statements is true (in and of themselves).

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19. ### arfa branecall me arfValued Senior Member

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The statement: "Humans are logical" doesn't deny that humans are also illogical, or anything else.

If humans can be logical (in an assumed future), is it because they can have this temporary conditional state you mention? What's the condition? If it's more accurate to say "Humans are capable of behaving logically", where is the cause of this capability you speak of?

Was Euclid logical or was he capable of being logical, and what's the difference?

20. ### arfa branecall me arfValued Senior Member

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What about a statement like: "Humans are less than or equal to logical." ?

Or could we make the whole thing safer: "Humans have logical brains." If this statement is true, it's always true logically, time has nothing to do with it. We evolved, we became human, we have human brains which are logical in the same sense computers are. It is a statement about the history of the universe that is independent of when it emerged, and since it's true today, it always had a unit probability of being true from the beginning.

That's despite all the things that affected that evolution--the number of times we nearly didn't make it. If, in some future we don't make it, that was always going to happen too, but, we can only assign a probability to future events where the past looks fixed, logically.

21. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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"Are" implies a continuous state. The state of "being logical" can halt. In the same way "I am swimming" is true for a time and then halts.

Huh?
What's the "cause" of any mental capacity in humans?

Since Euclid was, to the best of my knowledge, human then I'd have to assume that he also behaved/ thought illogically at times. Thus he was capable of being logical and on occasion was.

"Less than or equal" is mathematical concept. Is "logical"?

And I disagree with this in exactly the same grounds as previously stated. All you've done is move one step back. It's not more factually true than "Humans are logical".

This is incorrect.
We CAN think logically at times. But we certainly don't do it all the time.
And I'm not sure agree that we're logical in "the same sense that computers are" without further definition from you on "how" computers are logical.

22. ### DaeconKiwi fruitValued Senior Member

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Going back to your previous point in the OP:
(1. If something is logically true, it has always been true.)

I will get my hair cut at some time in the next 12 months.
I might, or might not, change my hair colour at some time in the next 12 months.

Would either of those two statements be logically true?

[edited for clarity]

Last edited: Aug 18, 2015
23. ### DywyddyrPenguinaciously duckalicious.Valued Senior Member

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That question was to me or Arf?

Edit: Oh, I assume it's referring to the OP.