Propositional Logic, Truth Tables, and Epicurus' Objection to "Dialectic"

  • Quote from Cassius

    What we are trying to do ultimately is get a firm fix on what it was that Epicurus was rejecting, while still embracing "reason" in PD16!

    All this discussion of details is irrelevant and worthless unless we keep that goal in mind.


    But even more important is to understand what Epicurus was proposing! It would be great to have a presentation discussing that; I've found it quite a challenge sorting through Methods of Inference. I would find it extremely useful, and would be quite grateful, if someone with more knowledge of the subject than I have could put something together.

  • But even more important is to understand what Epicurus was proposing!

    Right -- I think the two go hand in hand.

    A lot of this comes down to the struggle as to whether to consider the senses to be adequate to reveal reality to us, or whether we need something more (divine revelation, or the analogous "dialectical logic"). The Platonists and adherents of propositional logic want to consider the results of their calculations to transcend the reality of our senses, but in truth it doesn't, and is dependent on the reality of our senses to be relevant to us.,

    Ultimately I think we can get a good glimpse by seeing what Lucretius is focusing on in the key section of Book 4, starting around line 470. Knowledge, including all valid rational analysis, is ultimately based on the senses.

    So when you combine emphasis on the senses as our realm of reality and you layer on the passions (pleasure and pain) as the ultimate test of what "matters" to us then you've got a prescription for a full and complete approach to determining all truth that is relevant to us, Then when you add in the rejection of necessity (especially when it involves animate agency) you reject the gamesmanship involved in any kind of dialectical logic (which has nothing to do with any of those) because you always insist that the test of truth goes back (regardless of abstract formulas) to what we sense, pain/pleasure, and how we "anticipate."

  • I think that this much is pretty clear. Is this all that Philodemus is saying in Methods of Inference, or is he putting Epicurean reasoning into more formal terms?

  • Probably better to say that he is responding to formal arguments about why Epicurean reasoning is insufficient by pointing out that all methods of verifying the truth of arguments based on formal logic ultimately themselves trace back to the senses / canonical faculties.

    That sentence I keep highlighting in Delacy I think is most illustrative: The non-Epicurean Greeks allege that nothing can be confidently considered to be true unless you can supposedly validate the assertion through propositional logic.

    The flaw in that argument is, as we discussed, that the propositions have no inherent "necessary" connection to true reality, so that all attempts to verify any logical proposition ultimately depend upon the senses.

    In addition, the question arises as to under what circumstances an EPICUREAN is justified in asserting the truth of any assertion that cannot be verified through the senses themselves (such as assertions about places you have never been before).

    The opponents allege that propositional logic is the best way to make assertions about issues such as that.

    Philodemus argues that sufficient confidence can be attained in assertions about things which have never been experienced based on principles of analogy, without the use of dialectical logic.

    That's the reference by Diogenes Laertius this way, where he emphasizes "analogy, similarity, and combination" - means which are unrelated to propositional logic. If I recall Philodemus goes into a number of examples, or at least emphasizes this argument, as the proper response to reliance on propositional formal logic:

    Logic they reject as misleading. For they say it is sufficient for physicists to be guided by what things say of themselves. Thus in The Canon Epicurus says that the tests of truth are the sensations and concepts [preconceptions / anticipations] and the feelings; the Epicureans add to these the intuitive apprehensions of the mind. And this he says himself too in the summary addressed to Herodotus and in the Principal Doctrines. For, he says, all sensation is irrational and does not admit of memory; for it is not set in motion by itself, nor when it is set in motion by something else, can it add to it or take from it. Nor is there anything which can refute the sensations. For a similar sensation cannot refute a similar because it is equivalent in validity, nor a dissimilar a dissimilar, for the objects of which they are the criteria are not the same; nor again can reason, for all reason is dependent upon sensations; nor can one sensation refute another, for we attend to them all alike. Again, the fact of apperception confirms the truth of the sensations. And seeing and hearing are as much facts as feeling pain. From this it follows that as regards the imperceptible we must draw inferences from phenomena. For all thoughts have their origin in sensations by means of coincidence and analogy and similarity and combination, reasoning too contributing something. And the visions of the insane and those in dreams are true, for they cause movement, and that which does not exist cannot cause movement.

    (I gather that "apperception" is intended to refer to repeated perceptions, indicating that what confirms the truth of a single sensation is the repeated experience of the same perception under the same conditions.)

    You get into issues here too that I think are related to Frances Wright. She ended up (wrongly I think) taking the position ultimately that NOTHING but observation is significant - that you should never develop any conclusions or theories based on those perceptions, you should just trace one perception after another so long as you remain interested. I think Philodemus is a good place where we see that that was not Epicurus' position: Epicurus was apparently very willing to embrace theories about things which cannot be perceived (such at atoms) despite accepting that he had never and will never perceive them. He avoids improper dogmatism by accepting that sometimes we have to "Wait" and sometimes we have to accept multiple possibilities without choosing between them. But I think the point that Philodemus shows is that Epicurus did not go Frances Wright's extreme.

    What's left of "On Methods of Inference" seems designed to argue that Epicurean theory is that under proper conditions we can and should reach inferences (opinions as to what is true) about things which cannot be perceived directly.

  • I look forward to having my commentary picked apart and corrected so I can get it better myself, but that's the best I can do at the moment.

    The reason I think this is so profoundly important is that it is the ultimate resting point for the assertion that there is no "right" and "wrong" in the abstract. And unless we are a direct descendant of Nietzsche that attitude is what we were taught by our parents no matter whether they were snake-handling bible-banging rightists or Marxist humanist leftists. Everyone wants to enshrine their perspective in some kind of transcendental justification, and it seems to me that Epicurus is the most aggressive opponent of every variant of that.

    In Epicurus' time it was stoicism and platonism vs standard Greco-Roman religion and even eastern mysteries including Judaism.

    In our time the labels have changed but the attempt to justify one size fits all rules continues with just as much force, and maybe more , as it is now backed with modern technology and. Instant communication that triples down on the peer pressure.

    As I see it Epicurus is the only philosophy who offers a reasonable and even compelling worldview that stands in opposition to that transcendental - idealist attitude

  • I second your last statement Cassius! And I don't see anything to pick apart in your commentary. What I'm trying to discern is whether there are any Epicurean formulas comparable to the formulas for various types of logic. These would be useful both for discussion with non-Epicureans, and also for practical decision making. Personally I find the Canon very useful, as well as considering pleasures and desires in my decisions; I'm just curious as to whether there is evidence of "formulaic" reasoning in Philodemus.

    I'll need to wade back into OMOI, but I won't be getting to it for awhile. I can only take it in small doses before I get lost in the terminology ?(

  • Another point as to the significance of what we are talking about:

    It seems to me that a good case can be made that Plato's entire form of argument is encompassed within this term of "dialectic." Epicurus was objecting not just to conclusions, but to the entire "logic-based" approach.

    So for example we have Plato's Philebus, which is one of the primary Platonic dialogues arguing against the view that pleasure is the guide of life. We have dialectical exchanges such as this:

    So what I have argued before, and will still argue, is that an argument against Pleasure as the goal such as this needs to be approached on two levels:

    (1) You can point out that these propositional classes that Plato is throwing around - here, (1)"those things that have a limit," and (2) "those things that do not have a limit" in that there can always be more or less of them - have to be tied to reality in order for them to have any significance to us. "Tying them to reality" means verifying them through the canonical faculties (senses, passions, anticipations). That's a general way that you can respond to any propositional reasoning, by diving into the definitions and questioning those.

    (2) You can opt out of this entire line of reasoning by taking the position cited by Torquatus: "This Epicurus finds in pleasure; pleasure he holds to be the Chief Good, pain the Chief Evil. This he sets out to prove as follows: Every animal, as soon as it is born, seeks for pleasure, and delights in it as the Chief Good, while it recoils from pain as the Chief Evil, and so far as possible avoids it. This it does as long as it remains unperverted, at the prompting of Nature's own unbiased and honest verdict. Hence Epicurus refuses to admit any necessity for argument or discussion to prove that pleasure is desirable and pain to be avoided. These facts, be thinks, are perceived by the senses, as that fire is hot, snow white, honey sweet, none of which things need be proved by elaborate argument: it is enough merely to draw attention to them. (For there is a difference, he holds, between formal syllogistic proof of a thing and a mere notice or reminder: the former is the method for discovering abstruse and recondite truths, the latter for indicating facts that are obvious and evident.) Strip mankind of sensation, and nothing remains; it follows that Nature herself is the judge of that which is in accordance with or contrary to nature. What does Nature perceive or what does she judge of, beside pleasure and pain, to guide her actions of desire and of avoidance?"

    So arguably Epicurus is telling people not even to engage in propositional logic of the dialectical sort given its propensity to be confusing and easily tending toward manipulation in the hands of skillful people (like Plato).

    But I don't think Epicurus relied solely on "don't do dialectical argument." Just like we did in Martin's presentation, it is readily possible - for those who are so inclined - to dig into the premises and point out that the propositions are not consistent with reality. You can then restructure the propositional formulas into forms which more accurately approximate reality. But even there you have to keep in mind that it will only be an approximation of reality, and no matter how strong your formulation may appear, it will never be universally applicable to all people at all places and at all times. The entire structure of propositional logic is itself limited in what it can do, and that always has to be kept in mind or you'll get seduced by the apparent power of the propositional forms.

    (More or my cites on this issue are here: The Full Cup / Fullness of Pleasure Model )

  • Blunders during my presentation

    As mentioned and corrected in my additions and during the presentation, the truth table for OR on Slide 11 of the tutorial is wrong. While presenting, I wrongly mentioned that the examples on Slide 12 were wrong, too, but no, I merely got confused by the "ands" in the text. The examples for OR are correct.

    My second blunder was to wrongly identify q as a premise at the beginning of my explanation of Slide 13. I corrected it immediately but the confusion may have lead comments off track.

    The motivation for making the presentation was to show that a false premise in a syllogism does not necessarily mean that the conclusion is false, too. This mistake is easily made because often it is actually the case that the conclusion is false, too. That experience may misguide our intuition. Toward the end of my presentation, I made my third blunder by myself making that false inference to call a conclusion false upon finding a premise of an implication to be false but became aware of it only after the session. So, we need to make sure that my withdrawal of that statement accompanies the podcast.

  • On dialogical logic

    C. F. v. Weizsaecker's uses dialogical logic to justify usage of statements on the past in logical arguments in the book which I mentioned as reference in comment #10. (That justification does not work for statements on the future.)

  • Martin after I finish editing this week's podcast I am going to turn to editing this presentation. I want to get it out as soon as possible but there's no deadline or schedule so we will take as much time as we need to get it right. Before we release it to the public at all I will post it for the participants to review first, and we will make sure that we get it into good form before going further.

    We can even talk about doing another session to record over from scratch, but I think if we edit properly, and I insert some good caveat material as an introduction at the beginning, we can get something well worth using.

    I know myself that I make mistakes all the time and we can't let the "perfect be the enemy of the good" or else we wouldn't be here today having come as far as we have. We'll explain any misstatements that we leave in, and we'll also emphasize that just like with postings on the board people have to be free to change their minds, learn new ways to state things, etc.

    I just appreciate how much effort you've put into this already, and I am confident that by us all working through these issues - mistakes and all - the final conclusions and implications of this information will become much more clear.

  • Cassius

    Changed the title of the thread from “Special Presentation on The Limitations Of Formal Logic - The "Truth Table" Example” to “Propositional Logic, Truth Tables, and Epicurus' Objection to "Dialectic"”.
  • That I sometimes say "aeh" was known to me but not that I did it that often during the presentation. It sounds terrible and must be annoying to listeners.

    Another blunder was that while explaining a truth table, I repeatedly said "column" instead of "row".

    I suggest to remove the following passages:

    7:58 - 11:02 (detour on quantum and fuzzy logic)

    25:26 - 25:38 (wrong statements about Slide 12)

    25:50 - 26:32 (my confusion about premise and conclusion)

    around 27:17 ("I mixed them up" because if 25:50 - 26:32 is removed, it does no more apply)

    28:53 - 28:58 (another reference to my confusion)

  • Note: Martin's post there is referring to a preliminary edit, so when a version is posted to this thread the parts he is suggesting be taken out will not appear. I also note that while I do remove particularly long strings of "ahs" in the editing process, I don't attempt to remove them all in Martin's case because I find them a positive part of his German accent that actually adds to the full effect rather than detracts. If anyone has suggestions on how I can improve editing of the final released versions of this or the podcast please post or feel free to private message me.

  • In looking up Chrysippus this afternoon I see that there is material on Wikipedia relevant to this discussion:

    This below is not immediately relevant, but a good reminder for anyone who isn't aware of it and how it plays into Chryssipus' thinking:

  • Assuming that the Wikipedia section on Chryssipus' syllogistic correctly describes what he wrote, he certainly knew how to apply logic but he did not have a deep understanding of logic.

    His "indemonstrables" are very well demonstrable because they are well known theorems of logic, which can be proven e.g. by truth tables. There is no point in using them as axioms because they are proven theorems and therefore readily available for further proofs.

    His syllogistic seems to be a regression to times before Aristotle. It is not wrong but a detour in the history of philosophy and for the dust bin.

  • Ok before I start circulating this link to the world and only afterwards find some fatal flaw, please have a look at Release Candidate One of the Propositional Logic video featuring Martin's presentation from September 20, 2021.

    The formal presentation begins at 4:20. If you would like to skip the formal part and go straight to the conclusion and the panel discussion, skip to 44:00.

    (See below for Release Candidate Two)

  • Thanks for adding Slide 5 in the introduction. However, the spelling of my family name is wrong. Please correct to "Huehne".

    At the cut around 9:26, something is missing.

    At the cut around 10:19, something is missing.

  • Release Candidate Two:

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  • I am sure that this "release candidate two" probably still has some bugs in it, but I am thinking the big ones (misspelling Martin's name in particular!) have been corrected, so I will likely post this to the Facebook group and perhaps other places later this week.