Check it out.

Not bad! Although it is well to remember that some arguments may be good even though they are not actually [i:ca2c821e3e]logically valid[/i:ca2c821e3e].

:wink:

Rocketboom on Reasoning and Logical Fallacies

Check it out .

Not bad! Although it is well to remember that some arguments may be good even though they are not actually logically valid.

:wink:

Logical validity is a very tight straightjacket. Any argument of the type:

X’s fingerprints on the door
X’s motive
X’s method
X’s lacking alibi
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X did the crime

... is not logically valid. This is nonetheless structurally identical to the way scientists work when they give a so-called “inference to the best explanation”. That explanation is not logically forced by the evidence, but it is the one that seems simplest and most elegant.

Further, it is a good argument to say:

Most scientists who study X believe Y
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Y is true

E.g.: most biologists believe in Darwinian evolution, therefore Darwinian evolution is true. (Or, it should be believed true).

But—nota bene!—this is only a form of the fallacious argument of “appeal to the majority” or “appeal to authority”.

This is one reason why I think people who teach classes in critical thinking should go very easy on these supposed fallacies. They are fallacies of logic, not necessarily fallacies of argument.

Your examples are certainly not deductively valid, but how do you define inductive logic, Doug?  It seems that they would fit into that framework.

Occam

[quote author="Occam"]Your examples are certainly not deductively valid, but how do you define inductive logic, Doug?  It seems that they would fit into that framework.

Good point, and perhaps they would. But my point is rather that the standard fallacies are fallacies of deductive logic, and whatever else one may say about the virtues of induction, it is not deductively valid.

Every swan I have seen up to now has been white
---------------------
Every swan is white

... is not a deductively valid argument. This should be obvious, since there is no contradiction in its being false—e.g., there might be black swans on an undiscovered island somewhere. (As in fact there are black swans).

Fallacies of “appeal to majority” or “appeal to authority” might actually be inductively valid ... depends on whether they have been probabilistically accurate in the past ... !

I think some of the classical critical thinking fallacies have a partial liklihood of truth or of having some degree of truth.  It’s important to recognize their lack of rigorous deductive logic, but that doesn’t mean we should discard them without further consideration. 

Most of science is probabalistic and subject to modification, not given to the certainty of deductive logic, however, if we ignore all of the life experience, we can’t really arrive at many non-obvious conclusions.

Occam

Absolutely.

[quote author="dougsmith"] But my point is rather that the standard fallacies are fallacies of deductive logic, and whatever else one may say about the virtues of induction, it is not deductively valid.

Every swan I have seen up to now has been white
---------------------
Every swan is white

... is not a deductively valid argument. This should be obvious, since there is no contradiction in its being false—e.g., there might be black swans on an undiscovered island somewhere. (As in fact there are black swans).

(law of non-contradiction?)
Right, induction is the logical move of identity from a paticular to the universal. “I have seen a thousand apples and they were all red (particular examples), therefore, all apples are red” (universal). Same thing as you mentioned about the swans and the discovery of black swans in Australia.

Deduction is the move from a universal to the particular..."All birds have feathers (universal). This creature has feathers, therefore, it is a bird (particular).

Fallacies of “appeal to majority” or “appeal to authority” might actually be inductively valid ... depends on whether they have been probabilistically accurate in the past ... !

Ad populum is invalid. The appeal to authority (ipse dixit) is only invalid when the “authority” in question is not actually an “authority” about the topic in question. Such as, “My friend is a physicist and he says Koi should not be kept in an aquarium but rather outdoors in a pond.”

The title of “physicist” is not a qualification alone to determine how best to care for fish or opine on the aquarium hobby lest they invoke chemistry and biology but yet that is not the primary concern of study for a physicist.

I only used the example of Koi because I was instructed by the “experts” not to keep Koi in a tank yet my Koi are doing just fine nonetheless going on 6 months. So much for my “authorities” both in person and on the net.

Regardless, that is an excellent link and any authority is subject to be challenged given the introduction of new evidence. Gotta luv the ideals of the Enlightenment and free thought.

[quote author="Occam"]
Most of science is probabalistic and subject to modification

Just to get my two cents in, I’m of the opinion all science hence all knowledge is based on probability and degree of certainty and subject to modification. For those who disagree, I just want to ask, “And what Sir/Madam do you do with new facts?”

not given to the certainty of deductive logic, however, if we ignore all of the life experience, we can’t really arrive at many non-obvious conclusions.
Occam

Inductive logic is antecedent to deductive logic so at the end of the day we must admonish the Socratic disavowel of knowledge I think. Some things “seem” true.......until they are falsified............which is the process of inductive logic then which a deductive claim is made based on the previous claims or findings.....yet at some point in time those claims may be falsified with further epistemic discovery and technology.

So yeah, it is a matter of how much confidence we can place on a certain claim or theory which is based on the evaluation of the evidence for such claims or theories. But it is a good thing that this is a part of the logical process of the scientific method.