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Old 06-08-2006, 12:45 PM   #1
John D Wilson
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I'm a fan of the Paleo Diet which I consider much like Dan John's "Meat, leaves & berries" diet. However, sometimes the way the justification for the diet is expressed jars my logical senses.

For example:

"If it's on the Paleo diet, it's good for you. Milk is not on the Paleo diet, therefore milk is bad for you."

This statement involves a vacuous implication. Wikipedia give a good example:

"If I am asleep, my eyes are closed.
I am not asleep, therefore my eyes are not closed."

I used milk as an example because I am fond of yoghurt and whey protein. I am not lactose intolerant, but limit my consumption of milk because of the high sugar (lactose) content.

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Old 06-08-2006, 12:51 PM   #2
Jesse Woody
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You're right, that's a logical fallacy. A more accurate description might be "Milk isn't within the scope of our evolutionary genetics, so at best, it's unnecessary, while at worst, it's semi-toxic"
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Old 06-08-2006, 01:07 PM   #3
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john - all you need to do is reverse your statements. that is, "milk is bad for you, therefore it's not part of the paleo diet." the logic is perfectly sound, it just may be that people are confused in their presentations of it.

the paleo diet doesn't just arbitrarily pick things to be bad and subsequently exclude them from the diet; the diet is created around what appears to be natural and therefore optimal for human health. human beings are the only animals who consume milk after infancy--there are a number of reasons, not just lactose intolerance, that milk and dairy in general are less than ideal foods for big kids, and this is why they are "bad"--and consequently why they're not in the paleo diet.
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Old 06-08-2006, 01:27 PM   #4
John D Wilson
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Greg - first, I did your DROM this morning. Good stuff about stiff.

Second, your statement is a tautology. Anything bad is not part of the Paleo Diet, which is the same as (a tautology) saying the Paleo Diet is only what's good for you.

I read "Neanderthin" which has the premise "anything you could eat if you were naked and all you had was a sharp stick."

Would a Paleo dieter consume anything which was not available to primitive hunter gatherers? Not trying to pick a fight. Seriously interested. Maybe I need a better reference that the one cited above.

Thanks
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Old 06-08-2006, 02:46 PM   #5
Neal Winkler
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John, you're two arguments are not equivalent.

In your first argument, if we let "A" stand for "it's on the paleo diet" and "B" stand for "it's good for you," then your first argument looks like this:

A-->B
~B
____
~A

Which is modus tollens, a logically valid argument, though logical validity does not ensure that the conclusion is true, but it does mean that if all the premises are true then the conclusion must be true.

In your second argument, if we let "A" stand for "I'm asleep" and "B" stand for "my eyes are closed," then it looks like this:

A-->B
~A
____
~B

Which is the logical fallacy of denying the antecedent. As you can see, the structure of your first paleo argument is different than your sleeping example, and does not commit the fallacy for the latter.
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Old 06-08-2006, 03:06 PM   #6
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uh... what neal said. i think.

my point is that, like any diet claims to do, the paleo diet prescribes avoidance of foods deemed "bad". those foods are on the avoid list because they are considered bad; they are not considered bad because they are on the avoid list. there's an important difference between those two.

a paleo dieter is trying to replicate as accurately as possible the diet of a paleolithic human--it's not entirely possible for a number of reasons such as the type of meat available, but it is possible to get pretty close. so yes, a strict paleo dieter, in ideal circumstances, would not eat anything that would not have been available to someone 10,000 years ago.

glad you like the DROMs.
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Old 06-08-2006, 03:15 PM   #7
Neal Winkler
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Ah, crikey, I read over your argument too fast John, it does commit the fallacy of denying the antecedent like your sleep example. Whoops...
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Old 06-08-2006, 03:38 PM   #8
John D Wilson
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That's good, cause I NEVER make misteaks!
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Old 06-08-2006, 03:39 PM   #9
John D Wilson
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Ah, crikey. First mistake this year.
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Old 06-08-2006, 05:28 PM   #10
Neal Winkler
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Sorry about that Greg, I made you think I was right! I got an A in my deductive logic class, really I did! :rofl:

John, you're absolutely right that the arguement you presented was flawed.

Try this one on for size:

Let...

E = We evolved to eat x
H = x is healthy
m = Milk

(x)(~Ex-->~Hx)
~Em
______________
~Hm

What this says in english is:

For all things, if we didn't evolve to eat that thing, then that thing isn't healthy. We didn't evolve to eat milk. Therefore, milk is not healthy.
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