## modus ponens, denying the antecedent, migraine cause

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### modus ponens, denying the antecedent, migraine cause

I'm not a very good logician and, at best, a mediocre philosopher of science, even though I love the latter (but hate the former); so, I could use some help figuring this out. Thanks.

I believe nightshades (tomatoes, potatoes, chili peppers, eggplant, tobacco) give me migraines.

Out of modus ponens, modus tollens, affirming the consequent and denying the antecedent, it makes the most sense to me in terms of modus ponens, and even more in terms of denying the antecedent. But philosophers of science, as far as I know, don't talk much about modus ponens, do they?

Modus ponens is both inferentially valid and makes sense to me:

If P, then Q.
P.
Therefore, Q.

If I eat nightshades (P), then I get migraines (Q).
Therefore, I get migraines (Q).

But denying the antecedent, though inferentially invalid, makes even more sense to me, and conforms most to my experience:

If P, then Q.
Not P.
Therefore, not Q.

If I eat nightshades (P), then I get migraines (Q).
I do not eat nightshades (not P).
Therefore, I do not get migraines.)

Modus tollens seems even worse to me:
If P, then Q.
Not Q.
Therefore, not P

If I eat nightshades (P), then I get migraines (Q).
I did not get a migraine (not Q).
Therefore, I did not eat nightshades (not P).

But Popper used modus tollens to reject the hypothetico-deductive model and get out of the inductivist dilemma, which utilizes the inferentially invalid "form" of affirming the consequent:

If P, then Q.
Q.
Therefore, P.

To my nightshade example, this is the worst choice to me because it's invalid and contrary to my experience:

If I eat nightshades (P), then I get migraines (Q).
I get migraines (Q).

This is a common problem for most people trying to figure out causes and effects in terms of consumption choices.

So, is modus ponens the best logical form for my experiment (does it even qualify as a scientific experiment or is it too "anecdotal"?)? And how do I best relate this to Hume's views on induction and cause and effect, especially in terms of my experience? It seems like a simple problem (Popper), or puzzle (Kuhn). I hate migraines. If nightshades cause me migraines, then I'll quit them. My test (although probably not severe enough by Popper's terms) was the elimination diet method, where you quit food X for a month (or more, in my case it was about three), then eat a bunch of it/them for a few days (I used to get a lot of migraines until I started eliminating things from my diet, and it bears future practice because I've eliminated other things in relation to migraines and other symptom--there might be another problem with this method because it might not account for tolerance phenomena, e.g., it might be that if you eat nightshades or food X frequently, then your body adjusts; that is, elimination dieting doesn't control for metabolic adaptation confounds).

Also, it seems to me that the way I phrase it could make a difference, but I can't think of a way to phrase it to fit modus tollens (and therefore falsifiable) or affirming the consequent (and therefore hypothetico-deductive).
landis

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### Re: modus ponens, denying the antecedent, migraine cause

It sounds like you don't have sufficient control over your situation to use such simple analytical methods.

In complex situations, one has to use statistical analysis to merely reduce the number of variables involved to the point wherein one can use simpler logic. When dealing with health issues, one must go to extreme methods to minimize the number of variables so as to get a reasonably significant statistical data base before analysis can even begin. And usually by the time one has gathered sufficient data, the outside environment has changed in so many ways even such extremes might not be enough. Perhaps they were using a new pesticide that year, a new chemical in the air that altered your physiology such that your P would finish a formula that leads to Q. But a few months later, or with the addition of a different water source, the whole problem goes away.

Many years ago, in a far, far away land, I went to such extremes; "only rice and water for 3 weeks", then added "one variable at a time" so as to test the effects of that one under those conditions. And of course, did the on and off thing with days in between at least 3 times so as to produce reasonably reliable results - under those conditions in that land at that time with my body in the condition it was in at that time. A few years later would have produced different results. As it was, I tested about 30 different herbs and foods against that backdrop.

In a more chaotic environment even that wouldn't have worked to tell me anything useful. Simplification is the key along with an awareness that there are far more things changing around you in far more insidious ways than you really want to believe. Every change you make has a far greater probability of causing more trouble than curing any trouble. Your body learns to deal with almost anything consistent. If you keep changing things or others change them for you, neither your mind nor body can properly cope. You become entirely and insidiously dependent upon those doing the changing (the whole point in such changing).

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The Wise gather together to help one another in EVERY aspect of living.

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The only absolute certainty is formed by the absolute lack of alternatives.
It is not merely "do what works", but "to accomplish what purpose in what time frame at what cost".
As long as the authority is secretive, the population will be subjugated.

Amid the lack of certainty, put faith in the wiser to believe.
Devil's Motto: Make it look good, safe, innocent, and wise.. until it is too late to choose otherwise.

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### Re: modus ponens, denying the antecedent, migraine cause

Seems to me, landis, like you're going about this all wrong--I think this abstract contemplation on the logic of your experimentations is a red herring; keep it simple--the way you described your plan for experimentation would do just fine:

landis wrote:If nightshades cause me migraines, then I'll quit them. My test (although probably not severe enough by Popper's terms) was the elimination diet method, where you quit food X for a month (or more, in my case it was about three), then eat a bunch of it/them for a few days...

But since this is a philosophy forum, why don't we address your concerns over the logic of this whole thing.

landis wrote:But denying the antecedent, though inferentially invalid, makes even more sense to me, and conforms most to my experience:

If P, then Q.
Not P.
Therefore, not Q.

If I eat nightshades (P), then I get migraines (Q).
I do not eat nightshades (not P).
Therefore, I do not get migraines.)

I had an interesting discussion about the logic of conditionals recently: viewtopic.php?f=1&t=185298.partial

Essentially, the only reason why the above is inferentially invalid is because eating nightshades may not be the only thing that gives you migraines. Hangovers might do it; getting bashed over the head with a baseball bat might do it.

The reason why denying the antecedent seems to work for you is that all this stuff is implicitly assumed--you're not just thinking that abstaining from nightshades will eliminate your migraines but also abstaining from a night of heavy drinking, or getting bashed over the head by a baseball bat, plus anything else that might give you migraines.

landis wrote:Modus tollens seems even worse to me:
If P, then Q.
Not Q.
Therefore, not P

If I eat nightshades (P), then I get migraines (Q).
I did not get a migraine (not Q).
Therefore, I did not eat nightshades (not P).

Yeah, what's wrong with that?

landis wrote:But Popper used modus tollens to reject the hypothetico-deductive model and get out of the inductivist dilemma, which utilizes the inferentially invalid "form" of affirming the consequent:

If P, then Q.
Q.
Therefore, P.

Is this what Popper did? I don't get it.

landis wrote:To my nightshade example, this is the worst choice to me because it's invalid and contrary to my experience:

If I eat nightshades (P), then I get migraines (Q).
I get migraines (Q).

Right, which is another way of explaining why your example above about denying the antecedent seems to work for you: just because you get migraines doesn't mean you must be eating nightshades--as I said above, your migraines could come from a whole swack of different things.

landis wrote:(I used to get a lot of migraines until I started eliminating things from my diet, and it bears future practice because I've eliminated other things in relation to migraines and other symptom--there might be another problem with this method because it might not account for tolerance phenomena, e.g., it might be that if you eat nightshades or food X frequently, then your body adjusts; that is, elimination dieting doesn't control for metabolic adaptation confounds).

I think you're getting ahead of yourself here. Let's not assume tolerance comes into play at first. If you find that abstaining from nightshades eliminates your migraines, problem solved. If not, then try the test again controlling for tolerance.

landis wrote:Also, it seems to me that the way I phrase it could make a difference, but I can't think of a way to phrase it to fit modus tollens (and therefore falsifiable)

Modus Tollens wouldn't falsify anything.

If I drink poison, then I'll die.
I'm not dying.
Therefore, I didn't drink poison.

This does not falsify the claim that drinking poison causes death.

landis wrote:or affirming the consequent (and therefore hypothetico-deductive).

I don't think there's any logical way of putting it in terms of affirming the consequent. Like I said, affirming the consequent only seems to work because you're bringing in a bunch of implicit assumptions.
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gib
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### Re: modus ponens, denying the antecedent, migraine cause

gib wrote:If I eat nightshades (P), then I get migraines (Q).
I did not get a migraine (not Q).
Therefore, I did not eat nightshades (not P).

Yeah, what's wrong with that?
He might get migraines from something else. P is not saying that the only way he gets migraines is from eating nightshades, so the conclusion is false in general, though it might be right in his case.

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### Re: modus ponens, denying the antecedent, migraine cause

Moreno wrote:
gib wrote:If I eat nightshades (P), then I get migraines (Q).
I did not get a migraine (not Q).
Therefore, I did not eat nightshades (not P).

Yeah, what's wrong with that?
He might get migraines from something else.

But the minor premise is saying he didn't get a migraine.

Moreno wrote:P is not saying that the only way he gets migraines is from eating nightshades, so the conclusion is false in general, though it might be right in his case.

The conclusion is that he did not eat nightshades. If eating nightshades is supposed to give him headaches and he doesn't have a headache, then he must have not eaten nightshades.

Now, I realize that logic paints things in a very black and white manner, and I don't think real life works that way. Therefore, I can see how the conclusion drawn above may, in some cases, be false. When he says "If I eat nightshades, then I get migraines," he might mean nightshades usually give him migraines or that 99% of the time they do, or perhaps on occasion nightshades give him minor headaches which he doesn't consider strong enough to be migraines. If that's the case, then sure it's possible for him to eat nightshades and not get migraines, but he certainly said, in the minor premise, that he didn't get a migraine.
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Is that a demon slug in your stomach or are you just happy to see me?
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That's earth therapy. You might as well ask a horse to fix a merry-go-round. I mean, he'll try his best, but mostly, he's just gonna get horrified.
- Rick Sanchez

You're young, you have your whole life ahead of you, and your anal cavity is still taut yet malleable.
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gib
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### Re: modus ponens, denying the antecedent, migraine cause

gib wrote:
Moreno wrote:
gib wrote:If I eat nightshades (P), then I get migraines (Q).
I did not get a migraine (not Q).
Therefore, I did not eat nightshades (not P).

Yeah, what's wrong with that?
He might get migraines from something else.

But the minor premise is saying he didn't get a migraine.

Moreno wrote:P is not saying that the only way he gets migraines is from eating nightshades, so the conclusion is false in general, though it might be right in his case.

The conclusion is that he did not eat nightshades. If eating nightshades is supposed to give him headaches and he doesn't have a headache, then he must have not eaten nightshades.

Now, I realize that logic paints things in a very black and white manner, and I don't think real life works that way. Therefore, I can see how the conclusion drawn above may, in some cases, be false. When he says "If I eat nightshades, then I get migraines," he might mean nightshades usually give him migraines or that 99% of the time they do, or perhaps on occasion nightshades give him minor headaches which he doesn't consider strong enough to be migraines. If that's the case, then sure it's possible for him to eat nightshades and not get migraines, but he certainly said, in the minor premise, that he didn't get a migraine.

Oops. Man, did I not read that well.

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### Re: modus ponens, denying the antecedent, migraine cause

He has to realize that what he also did besides eating them might have canceled the effect they normally give. So even if he eats them and doesn't get a headache, he still doesn't have enough information to be conclusive with simple logic. Eating beans with rice makes a serious difference from eating beans alone. The rice completes a protein in the intestines which prevents gas production as well as reducing radicals that get in the blood of many people, but not everyone.

There are very many variables unaccounted for with such experiments making isolation of cause difficult to determine with certainty.
Clarify, Verify, Instill, and Reinforce the Perception of Hopes and Threats unto Anentropic Harmony
Else
From THIS age of sleep, Homo-sapien shall never awake.

The Wise gather together to help one another in EVERY aspect of living.

You are always more insecure than you think, just not by what you think.
The only absolute certainty is formed by the absolute lack of alternatives.
It is not merely "do what works", but "to accomplish what purpose in what time frame at what cost".
As long as the authority is secretive, the population will be subjugated.

Amid the lack of certainty, put faith in the wiser to believe.
Devil's Motto: Make it look good, safe, innocent, and wise.. until it is too late to choose otherwise.

The Real God ≡ The reason/cause for the Universe being what it is = "The situation cannot be what it is and also remain as it is".
.
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### Re: modus ponens, denying the antecedent, migraine cause

Moreno wrote:Oops. Man, did I not read that well.

Happens to the best of us, I guess.

It's funny how even the silly mistakes we make can lead into good discussion and new insights.

James S Saint wrote:He has to realize that what he also did besides eating them might have canceled the effect they normally give.

So like eating nightshades while popping a few pills of Tylenol? Sure, that could happen. But I think you can still do a thorough scientific investigation and get reliable results at the end of the day (although that might be a hell of long day).

landis seems to be saying that he gets migraines. He suspects that nightshades might be the culprit. There is a very simple test to see if there is a connection: go a few months without nightshades and see if the migraines disappear. If there is a confounding variable that happens to come up during these few months that might be having the effect of cancelling his migraines (ex. he, for some bizarre reason, decided to start a habit of popping T3s every morning at around the same time the experiment started--and this by sheer coincidence, landis not making the connection between that and the onset of the two months of his experiment), then we'll find out as soon as that confounding variable disappears. Once it does, and his migraines come back, then he'll know that a nightshade free diet does not cure his migraines and he'll know to look for another cause. But if the confounding variable doesn't ever disappear, well, what's the problem? He may be wrong to conclude that his migraines are caused by the nightshades, but he's free of migraines. So problem solved anyway.
My thoughts | My art | My music | My poetry

Is that a demon slug in your stomach or are you just happy to see me?
- Rick Sanchez

That's earth therapy. You might as well ask a horse to fix a merry-go-round. I mean, he'll try his best, but mostly, he's just gonna get horrified.
- Rick Sanchez

You're young, you have your whole life ahead of you, and your anal cavity is still taut yet malleable.
- Rick Sanchez

gib
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### Re: modus ponens, denying the antecedent, migraine cause

Holy crap. I posted this question on another philosophy forum and it got all heated instead of actually constructive like this. Thanks a lot contributors. This is sweet. I'm going to give the thread a read through or two then I'll get back to you all. Thanks again.
landis

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### Re: modus ponens, denying the antecedent, migraine cause

James S Saint wrote:It sounds like you don't have sufficient control over your situation to use such simple analytical methods.

Exactly. As gib put it:
gib wrote:Seems to me, landis, like you're going about this all wrong--I think this abstract contemplation on the logic of your experimentations is a red herring; keep it simple--the way you described your plan for experimentation would do just fine:

Yes, I was going about it wrong. And I wasn't just testing nightshades and migraines but the utility of Popperism for problems like this, which, as you rightly point out, overcomplicates matters.
James S Saint wrote:He has to realize that what he also did besides eating them might have canceled the effect they normally give. So even if he eats them and doesn't get a headache, he still doesn't have enough information to be conclusive with simple logic.

True. But I have enough data to satisfy my suspicions.
gib wrote:landis seems to be saying that he gets migraines. He suspects that nightshades might be the culprit. There is a very simple test to see if there is a connection: go a few months without nightshades and see if the migraines disappear. If there is a confounding variable that happens to come up during these few months that might be having the effect of cancelling his migraines (ex. he, for some bizarre reason, decided to start a habit of popping T3s every morning at around the same time the experiment started--and this by sheer coincidence, landis not making the connection between that and the onset of the two months of his experiment), then we'll find out as soon as that confounding variable disappears. Once it does, and his migraines come back, then he'll know that a nightshade free diet does not cure his migraines and he'll know to look for another cause. But if the confounding variable doesn't ever disappear, well, what's the problem? He may be wrong to conclude that his migraines are caused by the nightshades, but he's free of migraines. So problem solved anyway.

Bingo! Well put, gib. This is exactly what I did. I've done it with dairy and wheat for similar and varying symptoms. I'm reminded of Hume's A Treatise of Human Nature, Section XII, "Of the Probability of Causes," where he says:
Hume wrote:"What the vulgar call chance is nothing but a secret and concealed cause."
And reflecting on the rest of his most subtle philosophy in light of my consumption woes, it's helpful to use his scepticism to guide me in being satisfied with approximating a causal analsyis without controlling for all confounds, which is impossible. No?
landis

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### Re: modus ponens, denying the antecedent, migraine cause

There's a significant difference between "if" and "if and only if", or "iff" as it's also known. The step of denying the antecedent works only for iff P then Q.

"If I guess the right number in roulette, I win big at the casino" may be true, but you can still win big in other ways at the casino. "Iff I guess the right number in roulette, I win big at the casino" is only true for casinos that restrict their scope to roulette.

However, if eating nightshades (among other things) always give you migraines, it's fair to say that if you don't have a migraine, you haven't eaten nightshades (recently). So modus tollens is good there.

Wanting to find out whether nightshades cause it, in a complex multivariable situation like normal life, is a matter of statistics rather than logic. However, if you've ever eaten nightshades and not had a migraine soon after, you know that they don't all always cause migraines.

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### Re: modus ponens, denying the antecedent, migraine cause

Only_Humean wrote:...a matter of statistics rather than logic...
This is a false dichotomy as statistics is a form of inductive logic.
"Questions of reality are too important to be left to the scientists."
-Paul Feyerabend, The Tyranny of Science (p. 51; Polity: 2012).
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### Re: modus ponens, denying the antecedent, migraine cause

deleted (accidental replication)
"Questions of reality are too important to be left to the scientists."
-Paul Feyerabend, The Tyranny of Science (p. 51; Polity: 2012).
"Arguments seldom make converts in matters philosophical."
-William James, Principles (p. 468, v. 1)
"Argument is propaganda for one observer, the essence of human discourse for another."
-Feyerabend, Against Method (p. 236; Verso: 2010)
Blog: http://thislandismylandis.wordpress.com/
landis

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### Re: modus ponens, denying the antecedent, migraine cause

Land is, how have you been medicating? I have had similar, and addicted to all kinds of drugs, which over a period of time can prove dangerous or even lethal.

Then I discovered natural mess, thank god, they did make a huge difference.

Try Tumeric, fresh juiced with red grapes, with ginger, every day. In addition Tumeric tabs, 750 mg twice a day. Gave me almost total relief in two weeks , and as I am still new to the regimen, it may be still premature to say it a complete remission, (for I have had intolerable pain for the last 25 years), but so far so good. Will let you know with my success with it after I pass the thirty day mark.
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### Re: modus ponens, denying the antecedent, migraine cause

This thread is hilarious. The OP, landis, speaks in latin in attempt to obfuscate and complexify the sister of 2+2=4 in a fantastic manner.

Jerkee comes to the rescue, with down to earth english and a list of herbal remedies.
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### Re: modus ponens, denying the antecedent, migraine cause

Look, my answer to landis is this.
If you want to learn the truth of tomatoes...
Do the science, learn the scientific method, try learning how to program computer programs. Look less to latin and scholastic esotericism as your answer, and turn more to doing science and programming
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### Re: modus ponens, denying the antecedent, migraine cause

Not learning a bunch of latin to answer the equivalent of 2+2=4 type questions.

Could be a variety of things. Could be pesticides. You need a lab. And you need men in your lab. Women too. And you need to make sure your tomatoes are GMO free.

GMO's have tainted the ability of science to objectively test fruit and vegetables. The sample set has been polluted. It can never recover.
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### Re: modus ponens, denying the antecedent, migraine cause

Whhhhhaaaat? I was trying to help a pain sufferer, and others's advice is well suited, for migraine try not analyze, that may exerbitate the pain, rather, try something natural, earth giving. It takes migraine sufferers to know how devastating that is.

Let me ask this, Ha Ha, have you ever have had migraine? It can be devastating to the point, you can't move.

I may be making a service to her, as one human being to another. Remedies to pain transcend any philosophy, if they work.
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### Re: modus ponens, denying the antecedent, migraine cause

In my firm doctoral opinion, Landis' original post in itself causes a migraine.
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### Re: modus ponens, denying the antecedent, migraine cause

Ultimate Philosophy 1001 wrote:In my firm doctoral opinion

???
.. Ummm...
Clarify, Verify, Instill, and Reinforce the Perception of Hopes and Threats unto Anentropic Harmony
Else
From THIS age of sleep, Homo-sapien shall never awake.

The Wise gather together to help one another in EVERY aspect of living.

You are always more insecure than you think, just not by what you think.
The only absolute certainty is formed by the absolute lack of alternatives.
It is not merely "do what works", but "to accomplish what purpose in what time frame at what cost".
As long as the authority is secretive, the population will be subjugated.

Amid the lack of certainty, put faith in the wiser to believe.
Devil's Motto: Make it look good, safe, innocent, and wise.. until it is too late to choose otherwise.

The Real God ≡ The reason/cause for the Universe being what it is = "The situation cannot be what it is and also remain as it is".
.
James S Saint
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### Re: modus ponens, denying the antecedent, migraine cause

Well, fasting off everything besides nightshades will most certainly give you a migraine as the body dumps toxins..

As James noted, you need extreme conditions to isolate food variables..

To add to that, those extreme conditions can be indiscernable from what you are trying to figure out!

A catch 22

Turmeric is great advice - one of the best edible anti-inflammatories...

It's even good at preventing cancer

A study recently came out that inflammation is the highest known precursor to cancer
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### Re: modus ponens, denying the antecedent, migraine cause

That's cute only humean...

"If" implies "only if"...

There's not really a logical distinction

It's like saying "the" and "only the"

They both mean the same thing
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### Re: modus ponens, denying the antecedent, migraine cause

The: that which is implied

If: that which is hypothetically implied

They almost mean the same thing

They both imply singulars...

It's redundant to add a singular
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### Re: modus ponens, denying the antecedent, migraine cause

landis wrote:If P, then Q.
P.
Therefore, Q.

If I eat nightshades (P), then I get migraines (Q).
Therefore, I get migraines (Q).

But denying the antecedent, though inferentially invalid, makes even more sense to me, and conforms most to my experience:

If P, then Q.
Not P.
Therefore, not Q.

If I eat nightshades (P), then I get migraines (Q).
I do not eat nightshades (not P).
Therefore, I do not get migraines.)

This is false. You still may get migraines. For instance, you deny the antecedent, but a horse kicks you in the head. Bang, headache, logic is not applicable.

Modus tollens seems even worse to me:
If P, then Q.
Not Q.
Therefore, not P

If I eat nightshades (P), then I get migraines (Q).
I did not get a migraine (not Q).
Therefore, I did not eat nightshades (not P).

But Popper used modus tollens to reject the hypothetico-deductive model and get out of the inductivist dilemma, which utilizes the inferentially invalid "form" of affirming the consequent:

If P, then Q.
Q.
Therefore, P.

To my nightshade example, this is the worst choice to me because it's invalid and contrary to my experience:

If I eat nightshades (P), then I get migraines (Q).
I get migraines (Q).

This is also false. You may get a migraine from other than eating nightshades.

To make your dillemma and your belly-aching stick, you need to reword the original condition:
IFF P, then Q.
If and only if you eat nightshades, then you get a migraine.

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### Re: modus ponens, denying the antecedent, migraine cause

Ecmandu wrote:That's cute only humean...

"If" implies "only if"...

There's not really a logical distinction

It's like saying "the" and "only the"

They both mean the same thing

I think you read him wrong. He's pointing out the difference between, "if", and "if and only if". It's a necessity/possibility thing.
You see...a pimp's love is very different from that of a square.
Dating a stripper is like eating a noisy bag of chips in church. Everyone looks at you in disgust, but deep down they want some too.

What exactly is logic? -Magnus Anderson

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Mr Reasonable
resident contrarian

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