• 180 Proof
    14k
    There are no necessary truths; but that is not a necessary truth, it is just true.Bartricks
    Well, if you can, demonstrate that "there are no necessary truths" is true.
  • jorndoe
    3.2k
    In any possible world, a triangle will have three sides.

    Hence, it is necessarily true that a triangle has three sides.
    Banno

    Strictly speaking, shouldn't that be:

    In any possible world with triangles, a triangle will have three sides.

    ?

    Otherwise you might inadvertently have populated all possible worlds with triangles.

    Ed: was implicit
  • Bartricks
    6k
    Yes. Which is just an exotic way of saying triangles 'necessarily' have three sides. But Banno thinks it somehow proves the reality of necessity.
  • Bartricks
    6k
    I don't need to demonstrate that there are no necessary truths to show their dispensibility.

    But I can anyway:

    1. If God exists then there are no necessary truths
    2. God exists
    3. Therefore there are no necessary truths
  • Daniel
    458
    Hold your breath and see what happens when you are around one minute.
  • DingoJones
    2.8k
    As for not knowing what necessity is, I cannot comprehend what the word 'necessarily' corresponds to when it is added to true. So, a 'true' proposition is one that corresponds to the facts. What does a necessarily true one do?Bartricks

    Necessarily true refers to logical inference. It can be true that I am walking, and it would be necessarily true that I have legs to walk on. Its about logical sequence when you talk about something being necessarily true. If you are just talking about a specific instance of fact, the it would indeed be incorrect to use “necessarily” true.
    So if you adjust your understanding of those terms, you will see how the law of non-contradictions is violated in the concept of omniscience. Hopefully anyway, if Ive explained it clearly.
  • Banno
    23.1k
    You've got no idea. But you keep posting.
  • Bartricks
    6k
    Another way to say that would be that I have ideas none. Is there an SEP page on it that will enlighten me?
  • Bartricks
    6k
    no, that's not made anything clearer. But I am not confused and in need of enlightenment. I don't need to keep being told about necessity. I know it is invoked left right and centre and I know that the laws of logic are said to be necessary. I am saying that it adds nothing, isn't real and can be dispensed with.
  • Metaphysician Undercover
    12.3k
    I reject determinism because the notion invokes necessity. But that leaves open whether we have free will or not (which is what one would expect if necessity is doing no real work) as it leaves open whether we are originating causes of our decisions or mere links in a chain. It's the latter that seems to preclude our being free.Bartricks

    When you say "if those premises are true, then the conclusion will be as well", you are talking about judgement. If tThe premises are judged as true, then so will be the conclusion. What is that judgement based in if not the necessity of logic? Is it a free will judgement? In this case a person would be free to say that the conclusion will not be true

    .
    I can do something similar. Here: I stipulate that a valid argument is one that, if the premises are true then the conclusion is Potter true.Bartricks

    I think the point is that one judges the premises as true, for some reason. That reason need not be stated. So when they say that the conclusion of a logical argument is "necessarily" true, this is a statement as to the reason why it is judged to be true. It is judged as true because of the necessity which the logic produces.

    Rather than argue that "necessarily" has no purpose here, because it does serve a purpose, you'd be better off to look at the premises and ask why there is no qualification on the use of "true" in the premise. But wait, there is. It says "if" the premises are true, then the conclusion is necessarily true. So there's no problem at all. It says that if the premises are true, then the conclusion is necessarily true, where "necessarily" refers to the necessity produced by accepting the logic. If you reject the logic, which you could, of your own free will, then you would say that the conclusion is not necessarily true. Therefore "necessarily" clearly serves a purpose. It says that the judgement of truth assigned to the conclusion is dependent on acceptance of the logic.
  • Banno
    23.1k
    Is there an SEP page on it that will enlighten me?Bartricks

    Apparently not.
  • DingoJones
    2.8k
    no, that's not made anything clearer. But I am not confused and in need of enlightenment. I don't need to keep being told about necessity. I know it is invoked left right and centre and I know that the laws of logic are said to be necessary. I am saying that it adds nothing, isn't real and can be dispensed with.Bartricks

    So you do not understand, its not clear to you...yet you are still very certain that you aren't confused or need of enlightenment? Am I wasting my time, youre the preacher type not the learning/listening type? You arent even open to the possibility you are wrong here...its best to understand the opposing argument BEFORE concluding its wrong. You admitted yourself its not clear to you.
    The laws of logic are necessary to be logical. If you do not want to be logical then ok, but as i said as soon as you do then nobody knows what your talking about, including you. Discarding logic is a commitment to being non-sensical.
  • 180 Proof
    14k
    :smirk: Apparently ...

    ... assertion without a valid argument.
  • TheMadFool
    13.8k
    that's question begging. You've just stipulated that the whole point of logic is to 'prove necessary truths'. I am pointing out the redundancy of the word 'necessary'.

    You ask why should you accept my views - well, if they're true that gives you reason to accept them, no? Why do they have to be necessary truths?

    I mean, everyone accepts there are tons and tons of contingent truths - do you alone disbelieve them all?
    Bartricks

    You made a claim but I don't see an argument to back up that claim and if you had one, it would like like this:

    1.Blah blah blah (premises)
    So,
    2. There are no necessary truths (conclusion)

    2 has to follow necessarily from 1 to make your case i.e. given the premises, the conclusion must be a necessary truth. In other words, either you're making a baseless claim (begging the question) or you're contradicting yourself.
  • DingoJones
    2.8k
    You made a claim but I don't see an argument to back up that claim and if you had one, it would like like this:

    1.Blah blah blah (premises)
    So,
    2. There are no necessary truths (conclusion)

    2 has to follow necessarily from 1 to make your case i.e. given the premises, the conclusion must be a necessary truth. In other words, either you're making a baseless claim (begging the question) or you're contradicting yourself.
    TheMadFool

    Well said. Much better than the way I put it. (In one of the other threads about the same thing.
  • Bartricks
    6k
    You just keep putting the word 'necessary' in.

    I think you are confused about the kind of thing the rules of logic are. The rules of logic are instructions. They don't describe how we think, they 'tell us' how to think. So, we are told to believe that the conclusion is true if the premises are.

    Here's an instruction: if they have any butter, but me a pad of butter. That's an instruction and you can follow it. There's no necessity invoked. I am just telling you to do something under certain conditions.

    What if I said "if they have any butter, you must buy me some"? Well, that 'must' doesn't indicate the presence of necessity, but rather just serves to emphasize how much I want you to buy me butter.

    That's how things are with logic. We are indeed told that if the premises of a valid argument are true, then we 'must' believe the conclusion is true. But this does not indicate that necessity exists.

    To return to the point though: "if they have any butter, buy me some" and "if they have any butter, you must buy me some" are both instructions that one can follow. As such one does not need to be told that the conclusion of a valid argument 'must' be true in order to follow logic; that would be akin to thinking that you could only do as I say if I said "if they have any butter you 'must' buy me some" as opposed to just saying "if they have any butter, buy me some".
  • Heracloitus
    487
    Here's an instruction: if they have any butter, but me a pad of butter. That's an instruction and you can follow it. There's no necessity invoked. I am just telling you to do something under certain conditions.

    What if I said "if they have any butter, you must buy me some"? Well, that 'must' doesn't indicate the presence of necessity, but rather just serves to emphasize how much I want you to buy me butter.

    That's how things are with logic. We are indeed told that if the premises of a valid argument are true, then we 'must' believe the conclusion is true. But this does not indicate that necessity exists.
    Bartricks

    Logic deals with propositions. "buy me some butter", isn't a proposition. It's an imperative statement. Perhaps you should read up on what a proposition is, but for simplicity, it can be considered as the bearer of a truth/falsity value.
  • Bartricks
    6k
    No, they're instructions.
    Can you fail to follow a law of logic? Yes, of course one can - this is what happens when one reasons fallaciously.
    One 'follows' an argument. You can't follow a proposition. You can follow an instruction.
  • Heracloitus
    487
    No, they're instructions.
    Can you fail to follow a law of logic? Yes, of course one can - this is what happens when one reasons fallaciously
    Bartricks

    You have made it clear that you have not understood the subject and that you are unwilling to listen to others. I'll leave you to it.
  • Bartricks
    6k
    no, that's what you've just done. You just made the vague assertion "logic deals in propositions" (what does 'deals in' mean, exactly?).
    Then I replied with an argument that you are wrong. Here it is, in case you missed it:

    1. If you can fail to follow a law of logic, then the law is prescriptive
    2. You can fail to follow a law of logic
    3. Therefore, laws of logic are prescriptive.

    So, you - you - are the one who does not understand the subject they're confidently pronouncing on.
  • Heracloitus
    487
    Sigh. Logic as the analysis of the structure of arguments is centered around the notion of logical entailment. Logical entailment is the valid movement from premise to premise. .. to conclusion. Premises are propositions. They have truth value. I really don't feel like explaining basic propositional calculus.
  • Bartricks
    6k
    Which website did you copy and paste that from? You don't actually know what you're talking about, do you?
    Here's my argument again:

    1. If you can fail to follow a law of logic, then the law is prescriptive
    2. You can fail to follow a law of logic
    3. Therefore, laws of logic are prescriptive.

    Which premise do you deny?
  • Bartricks
    6k
    Shall I help you? A 'premise' is not a law of logic, right?
    Nor is a conclusion. When we say that the conclusion 'follows' from the premises, then we're appealing to a law, yes?
    The conclusion 'follows'......what does that mean? How can a conclusion 'follow'? Does it trail around after the premises? No, what we mean is.....that we are told to believe in the truth of the conclusion if, that is, the premises are true.
    That's a command. An imperative. When you make an inference you are attempting to follow such an imperative. Follow. Imperatives can be followed or flouted. The laws of logic are imperatives. Instructions. Prescriptions. That's why we try and 'follow' them. Sigh!
  • Heracloitus
    487
    It seems to me that your confusion is a result of conflating premises with the logical relation between premises. But its hard to make sense of your post.
  • Bartricks
    6k
    No, that's what 'you' are doing. The relation is a 'favoring' relation. And it is not between the premises and the conclusion, for premises, being propositions, can't 'favor' anything.

    Which premise in the argument I gave you do you deny? Or is the penny dropping that you might just not know what you're talking about and I might, just might, know exactly what I am talking about? "My confusion" indeed!! I am not remotely confused, I assure you.
  • Bartricks
    6k
    Here's the argument again:

    1. If you can fail to follow a law of logic, then the law is prescriptive
    2. You can fail to follow a law of logic
    3. Therefore, laws of logic are prescriptive.

    Which premise is false? Or is it sound? It's sound, yes?

    Prescriptions are relations. The premises are related to the conclusion by the prescription constitutive of a law of logic. We are told - instructed - to believe that if the premises of the above argument are true, then to believe the conclusion is true. The premises are not the instruction and nor is the conclusion or our act of believing it. The law of logic is the instruction. And it relates the premises to the conclusion and to us.

    But you're not listening at this point, are you? I'm just soooo confused, yes?
  • Heracloitus
    487

    I still think you have failed to see the distinction between premises themselves and their relations.

    Can you explain what you mean by "favoring relation"?

    "you can fail to follow a law of logic" is also nonsense statement. Can you reword it?
  • Bartricks
    6k
    Er, no. You're being tedious and you're out of your depth.
  • Metaphysician Undercover
    12.3k
    I think you are confused about the kind of thing the rules of logic are. The rules of logic are instructions. They don't describe how we think, they 'tell us' how to think. So, we are told to believe that the conclusion is true if the premises are.Bartricks

    Right, so "necessarily" means that you will judge the conclusion as true if you adhere to the rules, instructions.

    Here's an instruction: if they have any butter, but me a pad of butter. That's an instruction and you can follow it. There's no necessity invoked. I am just telling you to do something under certain conditions.Bartricks

    Clearly there is necessity invoked here. You are telling me that if they have butter then I need to get you a pad of butter, you are just not explicit with the "need". It's completely similar to the example of logic. I can of my own free choice, choose not to get you the butter, and this means that I do not see the need, just like you can of your own free choice choose not to follow the logic, and this means that you do not see the need. In the case of the logic we are explicit, using "necessarily".

    That's how things are with logic. We are indeed told that if the premises of a valid argument are true, then we 'must' believe the conclusion is true. But this does not indicate that necessity exists.Bartricks

    That's correct, but the issue you've brought up is whether or not "necessarily" serves a purpose, and it clearly does. It indicates that the conclusion is judged to be true only if you agree with the logical principles employed. So the "necessity" is within you, as the need to produce a conclusion. The judgement that the conclusion is true is contingent on you apprehending that need, just like me getting the butter for you is contingent on me apprehending the need. In the case of the logic we are explicit to describe what produces the need, the logical process. In the case of the butter you are not explicit as to why I need to get butter for you.

    To return to the point though: "if they have any butter, buy me some" and "if they have any butter, you must buy me some" are both instructions that one can follow. As such one does not need to be told that the conclusion of a valid argument 'must' be true in order to follow logic; that would be akin to thinking that you could only do as I say if I said "if they have any butter you 'must' buy me some" as opposed to just saying "if they have any butter, buy me some".Bartricks

    In the case of the logic, we are told that if we follow the logic we must accept the conclusion. In the case of the butter, there are many ways you could ask, "can you buy me some?", "please buy me some", etc.. Or, as you say "buy me some". They are all ways of asking. If I am agreeable, I will apprehend the need, and buy you some. You might also say "you must buy me some", and the same principle holds, you are still asking me to buy you some, and if I see the need, and am agreeable, I will.

    So, in the case of the logic we are given the reason we we ought to accept the conclusion. "Necessarily' represents the reason, which is that the logic backs up the conclusion. In the case of the butter you are not giving me the reason why I "must" buy you some. So the two are not comparable. With the logic "necessarily" gives reference to the logic, demonstrating the need. Unless you provide why I "must" buy you the butter, support the "must", as "necessarily" is supported by the logic, eg. you will die without it, then the "must" doesn't do the same thing as the "necessarily" does.
  • Bartricks
    6k
    I think you're missing my point. The word 'necessary' is ambiguous on everyday usage.

    If I say "it's necessary for you to buy me some butter" what do I mean? Do I mean that it is a necessary truth that you will buy me some butter? No, clearly not. I mean that it is urgent, important, imperative, that you do so. That's typically what words such as 'must' 'always' 'never' and so on mean when we use them.

    So, the language of necessity is used in everyday life not to describe the world, but simply to emphasize things - that is, it functions 'expressively'.

    But philosophers - most, anyway - think that there is this weird thing 'metaphysical necessity'. It's a strange glue that binds things immovably. So, a 'necessary truth', on their usage, is not a truth it is extremely important that you believe (which is what it'd be if the word 'necessary' was functioning expressively), but a truth that cannot be anything other than true - so a proposition that has truth bonded to it so strongly that it can never come away.

    Now, 'that' kind of necessity - metaphysical necessity - is the kind that I am suggesting we can dispense with. It is really just a case, I think, of us taking language that normally functions expressively, literally. As such we can dispense with it.

    I dispense with it - I don't believe in metaphysical necessity - yet I seem able to reason just as well as everyone else. It's just when I draw a conclusion, I think the conclusion 'is' true, whereas others will think that it is 'necessarily' true. But there's no real difference. It's not like there are two grades of truth. There are just true propositions and false propositions and a story to tell about how they got to be that way.

    Incidentally, if one thinks necessity does exist, then what I want to know is what the truth-maker for 'necessarily' true is.
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