• TheMadFool
    2.4k
    I just saw a video on youtube on the why of logic as in how one justifies one's belief in the system of logic as the correct method of thinking.

    1. It claims that to question logic is, itself, to be logical and therefore all criticisms of logic already subsume the principles of logic - we are looking for reasons to justify our doubts about logical authority.

    2. Others claim that to justify logic is to, again, assume logic's authority. This, they allege, is a circularity and therefore logic has no justification.

    So, it appears that we can neither justify nor critique logic. Both are circular.

    I feel like Buridan's ass right now.

    Please help...Thank you
  • Wayfarer
    6.6k
    Of course [one] is correct. Logic has to rest on something. It’s not controversial, although it never ceases to surprise how many people seem to think it’s fishy or suspect.

    That said, logic is not a form of omniscience. There may indeed be many things beyond logic, or for which logical analysis is unsuitable. But insofar as it is real, then the law of the excluded middle, or the law of identity, don’t need further justification - they simply are, they’re what Frege would regard as ‘primitive elements’, like natural numbers. If you ask why one and one equals two, the response can only be: just is so.
  • TheMadFool
    2.4k
    There may indeed be many things beyond logic, or for which logical analysis is unsuitable.Wayfarer

    Indeed. There must be some stuff out there in this universe or, may be, even inside our minds that transcends logic. Hyper-rationality (not irrationality) is a possibility I'm willing to admit.

    Of course [one] is correct.Wayfarer

    What about [two]? The problem still continues. May be we can make a choice which argument to accept. Both being circular and equal in all respects, one is left in an impasse. Can you come up with an analogy to better understand the situation?
  • Wayfarer
    6.6k
    If logic is circular - find another pastime.
  • TheMadFool
    2.4k
    This is a paradox of some kind isn't it - that we can neither argue for nor argue against logic?

    I see a way out though. Whether it's legit or not you can decide...

    The circularity of both attack/support logic prevents us from seeing the beginning. I guess that's where the action started and that's where we'll find the answer.

    So, what was/is the beginning of the circularity?

    It begins by questioning the authority or, more accurately, the rational basis of logic. In other words, one begins the circularity by questioning the validity of logic. To attempt to justify logic is also to begin from the same point - questioning the validity of logic.

    We could say that we begin by throwing doubt on logic in either case whether we try to justify logic or to criticize logic. Am I right?

    If I am right then it is clear that we begin not by attempting to justify logic but by attacking it. However, as I've just shown in the OP that isn't possible because it is self-defeating.

    Therefore, logic can't be criticized because that's a self-defeating process.

    Imagine a method x that is used to find truths. Now how does one know x is a truth? We would have to use, which is our situation, x to judge x. That would be circular yes but the problem began by questioning x using x itself and that is self-defeating.
  • BrianW
    235
    Why should logic be justified? Does it need justification? Doesn't logic imply justification? Do you mean 'how do we justify by logic?'

    Is it like, 'how do we determine that logic is logical?' I guess I don't know. Perhaps it depends with perspective. Then again, if that is so, it becomes subjective. Can logic be identified with either objectivity/subjectivity or does it encompass both?

    Quite the head-scratcher!
  • BrianW
    235
    I've been looking for a definition to logic. Something not in the dictionary; less linguistic and more of philosophy. Can we say that logic is a guide/path to reality/fact. This is because, if we claim that 'something' is logical, we probably mean, fundamentally, it contains an underlying truth, an undeniable fact. Therefore, could logic be that relation/connection, that path, between the 'something' and the truth?
  • jorndoe
    603
    Have you considered what would come of things, if we were to reject identity, the 1st law?

    • onto/logical: x = x
    • propositional: pp

    You may consider it a working presumption, if you like, which enables all kinds of things, including our talk.
  • ChatteringMonkey
    201
    Logic is about language only, and not about the world itself.

    Its justificiation lies in its use. It enables us to better understand the ramifications of what we say, and spot for instance contradictions in statements we make because of the law of identity.
  • TheMadFool
    2.4k
    Have you considered what would come of things, if we were to reject identity, the 1st law?

    onto/logical: x = x
    propositional: p ⇔ p

    You may consider it a working presumption, if you like, which enables all kinds of things, including our talk.
    jorndoe

    I guess denying the law of identity would make even the simplest discussion impossible.

    What of justifying logic as the authority among truth-finding methods? How does one do that?

    Perhaps self-justification isn’t wrong as such. I don’t know.

    Therefore, could logic be that relation/connection, that path, between the 'something' and the truth?BrianW

    What then justifies the validity of the path? Why believe in logic? Per logic we should withhold belief unless we have good reason.
  • Banno
    3.4k
    It’s worth noting that a circular argument is not invalid.
  • Wayfarer
    6.6k
    Logic is about language only, and not about the world itself.ChatteringMonkey

    If this were true, then deductive arguments would have no application in empirical science.

    However, deductive arguments do apply to empirical science.

    Therefore this is not true.
  • Banno
    3.4k
    indeed; as if language where not about the world.
  • Banno
    3.4k
    Logic is just good grammar.
  • Wayfarer
    6.6k
    That’s pretty right, but it’s also more than that. Logic would be impossible without abstraction and generalisation, which in turn are constituents of language itself [as well as arithmetic]. And then it turns out that logic can be used to discover, or disclose, things about the world that we wouldn’t otherwise know, which actually is a remarkable thing, that is often taken for granted.
  • BrianW
    235
    What then justifies the validity of the path?TheMadFool

    That it relates/connects to truth/reality is the justification/validation.
  • Banno
    3.4k
    That’s pretty right, but it’s also more than that. Logic would be impossible without abstraction and generalisation, which in turn are constituents of language itself [as well as arithmetic]. And then it turns out that logic can be used to discover, or disclose, things about the world that we wouldn’t otherwise know, which actually is a remarkable thing, that is often taken for granted.Wayfarer

    Perhaps. I see logic as well-structured language. So introducing conjunction, disjunction, negation and non-contradiction as formation rules gives us the capacity to reject arguments that do not lead to further disclosure. That is, formation rules express a preference for one sort of language over another; for language that works better.

    Given that we choose the grammar that works better over other grammars, its not that remarkable that we have a language that works.

    Hence language and logic are inseparable. Pretty much the same thing, really.

    And hence induction is not a logic; it's not a set of grammatical rules.

    And hence we can find other logics, such as the various modal systems as choosing other grammatical systems that can be accepted or rejected in terms of how well they work.
  • ChatteringMonkey
    201


    Logic is about language only, and not about the world itself. — ChatteringMonkey
    If this were true, then deductive arguments would have no application in empirical science.

    However, deductive arguments do apply to empirical science.

    Therefore this is not true.
    Wayfarer

    Your argument is valid, but not sound because the first premise is not true :-).

    Empirical sciences work with language too, so i don't see how it follows that deductive arguments wouldn't apply to it if logic were only about language.
  • andrewk
    1.6k
    I feel like Buridan's ass right now.

    Please help
    TheMadFool
    Buridan's ass was prey to indecisiveness that - hypothetically - caused it to starve.

    Do you think that your opinion on the topic in the OP will cause you to starve?

    Are you seriously considering abandoning the use of logic? If so, how would you go about doing that?

    If not, why do you feel you need help? It seems to me you're getting along just fine.
  • TheMadFool
    2.4k
    It seems to me you're getting along just fine.andrewk

    Thank you.

    It’s just that I’ve broached this topic many times (some others too) and no one has given me an answer that would give me closure.

    In the beginning I thought it was just the circularity of logic justifying itself. After the video on YouTube I realized even criticism of logic is impossible as it, well, uses logic.

    When somebody asks whether logic is justified or not, it is an attempt to find reasons that justify logic or to find reasons that make logic unjustified. As you can see both paths are rational i.e. logical.

    Isn’t the situation hopeless? I find it so.
  • TheMadFool
    2.4k
    Logic is just good grammar.Banno
    @Wayfarer

    Language is arbitrary and is, if you truly analyze it, a matter of convention. Languages differ from place to place and time to time but logic isn’t like that. Logic is kinda universal unlike language. What do you think is the reason for this? Thanks.
  • tim wood
    1.2k
    When somebody asks whether logic is justified or not,TheMadFool
    The answer my philosophy prof. gave to the question of "justifying" logic was that it worked "because it had better" work. And I think there's something to this. I hear in it the acknowledgement that the search for some - any - ultimate ground is futile and ultimately naive and un-mature, that the most one gets is efficacy.
  • TheMadFool
    2.4k
    The answer my philosophy prof. gave to the question of "justifying" logic was that it worked "because it had better" work. And I think there's something to this. I hear in it the acknowledgement that the search for some - any - ultimate ground is futile and ultimately naive and un-mature, that the most one gets is efficacy.tim wood

    Here’s a kinda-sorta “proof”:

    Logic’s justification can be grounded in its ability to find truths. Basically, if logic gets to truths then that’s a justification of its principles and ergo itself.

    The problem, of course, is that truth is assessed by the extent to which logical principles were adhered to. We say that a certain proposition is true because of a sound logical argument.

    So, we can’t rely on how good a truth-finder logic is to justify logic.

    Is there some other way then?

    How about this:

    Logic can be thought of as a hypothesis about how the world works. Very much like in the sciences.

    This hypothesis is that The world is Logical. This should entail some predictions about our world. We then check to what extent do our predictions come true. In fact every instance of the application of logic is a test of this hypothesis.

    Now we check if the predictions come true. If the vast majority (the actual truth is ALL logical predictions we’ve made so far except quantum mechanics) of our predictions come true then these serve as justifications for logic. It’s an inductive argument and short of the sound argument I’m looking for BUT it’s better than nothing right?

    My inductive argument in explicit form is as below:

    Hypothesis: The world is logical
    The above hypothesis makes predictions
    X% of the predictions are true
    As you can see as X approaches 100, as is the factual situation, we get a cogent argument that justifies logic.
  • ChatteringMonkey
    201
    Logic’s justification can be grounded in its ability to find truths. Basically, if logic gets to truths then that’s a justification of its principles and ergo itself.TheMadFool

    Logic does not strictly speaking 'find truth', it's truth-preserving. It's about making good arguments that preserve the truth value of the premises. A good argument is valid. A sound argument is a valid argument which has premises that are true. To determine the truth of the premises you do not use logic itself, you go and verify them with data, or in the case of analytic truth they are true by definition.

    So the justification is not that it finds truth, but that it explicates the further implication of truths, and shows you what are good and bad ways to go about that.

    Edit: And again, logic is not about the world, it's about language, about the abstractions we make about the world. For instance there no X that equals X in the world, nothing is entirely equal.
  • tim wood
    1.2k
    Here’s a kinda-sorta “proof”:TheMadFool
    And a pretty good one, imho. Now break it down and watch it evaporate even as you watch. The catch lies in the hypotheses and the presuppositions. It's all good if they're good - but are they good/good enough? I think they're not, and that it simply doesn't matter.

    Does your wife/girl friend/life partner love you? Do you poke at it every day to try to understand or prove it? (I hope not!) Of course not. It works, and that's the best anyone does, and the best possible.

    you might argue that logic itself is a posteriori, but that its functioning is a priori.
  • VagabondSpectre
    1.2k
    There's no star-spangled guarentee that logic will continue to yield "truth". It's a kind of brute fact that logic yields truth: inductive experience points to deduction as robust.

    Although, if things did not have consistent "logical" relationships, the world might be a much more surprising place to live in.

    When it comes to justifying induction, we can use more induction:

    In my experience, objects have consistency...

    In my experience, I consistently observe that objects have consistency...

    In my experience, I consistently observe that I consistently observe that objects have consistency...
  • mcdoodle
    995
    \I'm interested in inference, which is conventionally described as something inside logic, a step of reasoning.

    To my mind logic is a human construct. It has its own particular subset of language. I don't buy the idea of a closer relationship to 'language' in general than that.

    I see other animals, however, making inferences, about food, trails, whether you're an enemy or friend. I don't believe they have logic, or language. But they have inferential systems.
  • Banno
    3.4k
    That certain rules of grammar are better at producing results than others. These rules can therefore be found in a wide range of languages.
  • Banno
    3.4k
    Perhaps we could look at a counterexample to my thesis.

    "I never done nothing like that" - a double negative used to emphasis the negation rather than to negate it.
  • Moliere
    1.4k
    It seems to me that studying logic is something of an empirical matter that can then be formalized. Logic is that set of inferences which are truth-preservative -- so, assuming that our [elements] -- be they sentences, propositions, beliefs, frames, predicates, etc. -- are true, we will know that the conclusion from these elements is also true. It's something of an empirical matter in that we can study arguments, and formalize them. Usually the way to show that something is a fallacy is to come up with an example of an argument that uses the same form, but draws an obviously false conclusion -- hence, with that example in hand, we know that the form of argument is not truth-preservative, since we were able to derive obviously false conclusions using it.

    EDIT: One consequence of looking at logic like this is that we have to know something already before we can investigate logic. So it is not a foundation of knowledge, exactly, but something which comes after already knowing -- a generalization of knowledge we know now. Consequently it may be shown, with the more that we know, that some inferential step we once took as valid is shown to be invalid. Logic is something that lives and breathes and changes.
  • BrianW
    235
    It seems difficult to explain logic as an independent factor. Perhaps because it is too broad for the human capacity for knowledge to comprehend it fully. In a way, logic implies reason, inference, thinking, etc. However, there is something about all those aspects that is somewhat natural, inherent or instinctive to man and possibly to life.

    "Man is conscious of a universal soul within or behind his individual life, wherein, as in a firmament, the natures of Justice, Truth, Love, Freedom, arise and shine. This universal soul, he calls Reason: it is not mine or thine or his, but we are its; we are its property and men. And the blue sky in which the private earth is buried, the sky with its eternal calm, and full of everlasting orbs, is the type of Reason. That which, intellectually considered, we call Reason, considered in relation to nature, we call Spirit. Spirit is the Creator. Spirit hath life in itself. And man in all ages and countries, embodies it in his language, as the Father.
    It is easily seen that there is nothing lucky or capricious in these analogies, but that they are constant, and pervade nature. These are not the dreams of a few poets, here and there, but man is an analogist, and studies relations in all objects. He is placed in the centre of beings, and a ray of relation passes from every other being to him. And neither can man be understood without these objects, nor these objects without man. All the facts in natural history taken by themselves, have no value, but are barren like a single sex. But marry it to human history, and it is full of life. Whole Floras, all Linnæus’ and Buffon’s volumes, are but dry catalogues of facts; but the most trivial of these facts, the habit of a plant, the organs, or work, or noise of an insect, applied to the illustration of a fact in intellectual philosophy, or, in any way associated to human nature, affects us in the most lively and agreeable manner."
    From 'NATURE' by Ralph Waldo Emerson.

    This passage makes me think that perhaps within logic belies a universal principle, through which, we use to connect/relate to the many aspects of life. In this way, logic isn't something that is justified, rather, it justifies. It justifies truth as acceptable.
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