Re: "Friendly Premises"
- From: "George Dance" <georgedance04@xxxxxxxx>
- Date: 3 Aug 2005 08:37:53 -0700
geraldrm@xxxxxxxxxxxxx wrote:
> I have several questions concerning how logicians feel about "friendly
> premises" -- who discusses their use, what is the correct terminology,
> etc. I've read a great deal in books on logic for the layman but
> haven't come across anything that corresponds to this issue.
>
> By "friendly premises" I mean premises that people posit (often
> unstated) that are necessary to a theory they are building on
> circumstantial evidence. That is, they examine circumstantial
> evidence, construct a theory that pulls the circumstantial evidence
> together plausibly, but the proposal demands certain factual premises.
Speaking for myself, rather than logicians, I'd describe (and have
described) logic as a way to uncover and examine those premises. Logic
investigates 'valid' arguments or reasoning, those in which it's
impossible for the premises to be true and the conclusion false. Logic
alone cannot say which extraneous premises are false; only that if an
argument is valid, and its conclusion is false, at least one of the
premises is false.
Logic can tell you whether someone's argument for a theory is valid.
If it is, and there's a reason to think that the conclusion (the
theory) is false, that means there's also a reason to think that one of
the premises is false. If it is not, and there's reason to think that
the conclusion is false, there's reason to think that the theorist is
assuming unstated premises (which would give him a valid argument); and
at least trying to make those premises explicit by repairing the
argument so that it is valid.
> The author either avoids mentioning them and just praises the
> plausibility of his theory, or he mentions them but leaves it up to the
> reader to do the research to determine whether they are true or false.
If the author avoids stating all his premises, then he's given an
invalid argument (though it might appear valid to those who share the
same unstated premises). If one's corresponding with him (say, on
Usenet), one can point out that the argument is invalid; at which point
he can repair it himself by making his additional premises explicit.
If one's simply reading an author, the best one can do is try to
identify the hidden premises oneself.
If the author simply declares his premises as true, without supporting
them in any way, it becomes a matter of trying to discover his reasons
for believing them. (In either of the same two ways.)
> The author may even allege that there is no factual evidence available
> as to the truth or falsity of the premises, and hint that the friendly
> premises are probably true if their use leads to a theory that sounds
> plausible. Is that much clear?
The author cannot plausibly claim that any of his premises are true
*because*, as a consequence of them, his theory is true; that's nothing
but circular reasoning. He can claim that a premise is true because
it's necessary for the truth of some other theory (which the reader
also accepts); that can be a good inductive argument.
> My questions are as follows.
>
> 1. Does anyone discuss whose responsibility it is to check friendly
> premises? Does a proposer have the right to concoct a theory and
> praise its virtues without bothering to verify the truth of his
> premises?
He has a legal right of course; but not, I'd say, an epistemic one.
Someone who believes an assertion for no reason should not expect to be
taken seriously when he asserts it.
> 2. Proposers sometimes claim that the beauty or consistency or
> problem-solving ability of their theory validates their undefended
> friendly premises. But aren't there many cases where beautiful /
> consistent / problem-solving theories have later been proven to have at
> least one fallacious premise? Can you recommend anyone who discusses
> this or gives examples?
One applicable point, which I've read widely (but can't remember the
original source - I think it was Popper), is that any fact can be
explained by an infinite number of theories. So that a theory explains
a fact is not, by itself, a sufficient reason to believe the theory.
I'd see considerations of 'beauty' etc. entering in only where one has
two inconsistent theories which both fully explain the same facts. In
cases like that, eg, it's quite in order to choose between them on the
basis of criteria like Occam's Razor, believing the simplest one (the
one with the fewest premises) eg.
> My questions aren't purely theoretical. I'm trying to assess a
> scholarly proposal in an historical field that posits a bunch of
> friendly premises that the author considers verified by the
> plausibility of the theory he has built upon them. I'm not at all
> clear how to analyze the procedure or what are the correct logical
> terms involved.
To sum up, I'd say the correct procedure would be:
1) State the author's argument for the theory in semi-formal form (as a
list of premises and conclusion). Is the argument valid? If not, what
other premises would be required for it to be valid?
2) State the author's argument for each controversial premise in the
same form. Are those valid? If so, what are the premises for those
premises (the premises^2)?
3) If the author's only stated premise(^2) for any premise is that
without it his theory is incorrect, that's not a valid argument for the
premise. To be valid, it would have to be recast as a modus tollens
argument:
1. If premise X is not correct, then theory Y is not correct.
2. [Theory Y is correct.]
----------
3. Premise X is correct.
Which is a valid argument. However, if the author then goes on to
argue for theory Y on the basis of premise X, he's given nothing but a
circular argument.
Thanks in advance to anyone who responds.
[BTW, it may be just me, but I find that last a bit rude; it sounds
like, "I couldn't be bothered to write and thank you after you've
answered my question."]
.
- References:
- "Friendly Premises"
- From: geraldrm
- "Friendly Premises"
- Prev by Date: Re: Polish foundations?
- Next by Date: Re: "Friendly Premises"
- Previous by thread: Re: "Friendly Premises"
- Next by thread: Re: "Friendly Premises"
- Index(es):
Relevant Pages
|
