Critical Thinking: Premise and Evidence Acceptability, Unacceptability, and Uncertainty Revisited

Introduction
Up until now we've looked at the major components of argument, argument evaluation, and argument construction:  (a) premise acceptability and (b) logical force (which is made up of (i) premise relevance and (ii) sufficiency).  Now we are going to look at these elements a little more closely.

Premise/Evidence Acceptability
When it comes to value-based arguments (e.g., political, moral, and religious) we will often not be able to achieve 100% certainty of truth of the premises.  Even something as intuitively obvious like "it's wrong to kill innocent people" will have counter-examples.  However, simply because a premise cannot be 100% true in all cases, it doesn't necessarily mean that we should reject it or that the argument of which it is a part is poor.  Instead, it means we need to be subtle in our evaluations and consider carefully what the logical consequences are of accepting certain premises.

Recall from our previous discussion of premise acceptability that premises/evidence need to meet general two standards:  (1) would the intended audience accept the claims without further support? (i.e., do the premises take into account the audiences "cluster" of beliefs and values) and (2) are the claims acceptable to a "reasonable" universal audience.

Acceptability has much to do with burden of proof.  From the perspectives of both (1) and (2) we need to ask, (3) would these claims be accepted without anyone asking for more evidence?  And (4) is there no available information or evidence that we know of that contradicts the claims?  If the answer is "yes" to both, then the premise is acceptable.  If not, then it isn't, and the burden to provide further support rests upon the person making the argument.   An acceptable premise is one that passes both the intended audience and the reasonable universal audience test.

Going back to the reasonable universal audience test, if the answer is "no", then we would say the evidence is questionable.   Evidence/premises are questionable when they fail the "reasonableness" test but we still haven't come up with any direct contradicting claims.

For example, suppose I want to claim that it's an affront to the Olympic spirit that wrestling be removed from the Olympics.  We might point out that the phrase "affront the the Olympic spirit" is quite vague and could be variously interpreted.  So, in our evaluation of the acceptability we might say that the claim is questionable because its meaning is vague.

However, at this point we wouldn't yet be able to say that claim is unacceptable.  An unacceptable claim is one for which there is known evidence that directly contradicts the claim.  Since, in the wrestling case there isn't obvious evidence against the claim, it is not unacceptable, merely questionable.

If I were to claim that the moon is made of cheese, this claim would be unacceptable since there is known evidence that directly contradicts the claim.

The difference between a questionable and an unacceptable claim is that with the former, it fails the reasonableness test because we don't have enough information (maybe it's too vague); and with the latter there is known evidence that contracts the claim that a reasonable audience would be aware of.

The Nitty Gritty:  How Do We Know What a Reasonable Audience Will Accept?
For the most part this is an element of subjectivity here but there are main 2 guidelines we can begin with to determine if a reasonable audience would accept a claim: (A) The claim doesn't contradict any of the other claims made in the argument and (B) the claim could be defended in front of an audience comprised of a broad cross-section of society.  Of course, this still doesn't give us any mathematically precise formula for determining reasonableness but it a start.  In addition, here are couple more heuristics we can use to determine acceptability...

Acceptable By Definition or Self-Evidently Acceptable
Some premises are definitions.  Often, (but not always) definitions are considered self-evident or true by definition.  For example, a triangle is a three-sided figure or a bachelor is an unmarried male.  You can't argue with that.  Ain't nobody got time for that!  For definitions, the litmus test is what a community of language-users would accept as a definition for a term.

We can also have claims that are self-evident because they are logical truths, like "a thing cannot both exist and not exist at the same time."

Self-evident claims can also pertain to the moral realm (unless your audience is philosophers!).  Statements like, "causing unnecessary suffering is bad" or "killing innocent people is bad" are considered self-evident to a reasonable general audience.

Acceptable as a Factual Statement Reporting an Observation or as a Statement of Eye-Witness Testimony
Unless we are provided with some reason not to, we accept people's testimony about what happened to them or what they observed.  If someone said "it's sunny outside yesterday," you have no reason not to accept the claim. Also, if I told you that I was going to the store to get myself a cold pop, you should accept my claim at face value.

Of course, if I have a reputation of being a big fat liar, then you'd have reason to be skeptical of my claims.  Also, if what I said happened to contradict something else I'd said, then you would also have reason to question the acceptability of my claim.  But barring such situations, we take speaker observations and testimony at face value.

Acceptable by Common Knowledge or Assent
We have to be careful with this one because it can lead us to accept things uncritically that we probably shouldn't.   "Common knowledge" can be divided into 2 categories:  factual claims and value claims.  A factual claim would be something like, "the earth is a spheroid" or "Obama is the current president of the USA."  A value claim or value judgment would be something like, "it's wrong to hit children" or "we shouldn't allow people to starve."

So, where does acceptability fit into this?  Although we said previously that acceptability depends largely on what a reasonable member of a universal audience would accept, there are exceptions.  Concerning factual claims, if the intended audience has specialized knowledge (doctors, scientists, etc...) then it's OK to evaluate the claim in relation to the knowledge base we'd expect that group to have.

We might reply, but wait! What happens if the knowledge isn't known by every member of that audience?  In such cases, we can make assumptions about what factual knowledge we'd reasonably expect the members of a specific expert audience to have.

In all this talk of specific audiences, lets not lose sight of the "common knowledge by a universal audience" aspect of this criteria.  Just because some knowledge might be particular to a field of study or expertise, doesn't mean that there isn't knowledge that we can reasonably expect Joe Schmo to know.   Stuff like, "the third Batman movie was awful" or "grass is green" or "Las Vegas is the entertainment capitol of the world" are all things that we'd expect a general (North American) audience to know and so we can accept them at face value.   Similarly "Uzbekistan was part of the former USSR" is something we'd reasonably expect every general audience outside of the USA to know :)

Acceptable Because it is Defended in a Reasonable Sub-Argument
In Mill's proof of utilitarianism he makes the sub-claim that the general happiness is good to all humans.  This is on its face is not a claim that we'd expect a universal audience to accept.  However, Mill, knowing what a general audience might not accept, provides a supporting argument working from our particular desire for our own happiness to the more general claim.  

Since he supports his sub-claim with a reasonable argument we can now accept it.  (And consequentially turn our critical thinking toward the supporting sub-premises.)

When evaluating for premise acceptability, we can do the same with any sub-claim.  It it doesn't seem reasonable we can see if it is supported by a sub-argument.  If it is, and that sub-argument is reasonable, then we can accept the sub-claim.

Acceptable on the Authoritar of the Arguer or an Expert
We can broadly divide this criteria into two types:  uncontroversial claims made by an arguer and claims made by an expert.

In the first class these are claims about relatively uncontroversial things that the arguer might know about.  For example, I might say that the University of Houston has a good philosophy graduate program.  Because I've been there and you haven't, you have no grounds to doubt my claim and since it isn't particularly contentious, it should be viewed as acceptable.

In the second class we have claims made by experts.   This is known as an "appeal to authority".  This is when the arguer supports a claim by appealing to the expert knowledge of a person, institution, or source.  

A quick note here, the best appeals to authority are appeals to the consensus opinion of a community of experts.  Appeal to a single expert doesn't carry much weight, especially in controversial topics.  The opinion could easily be an outlier.

Conditions of Unacceptability
Unacceptable because of an Inconsistency
We might label a claim as unacceptable because it is inconsistent with other claims the same arguer has made.  For example, in alt-med we often see arguments stating that the flu vaccine shouldn't be used because its efficacy can sometimes be as low as 45%.  However, the northern Andean magic rainbow-berry or acupuncture they propose instead has no reported efficacy.  

So, if the argument is that we should reject a treatment because of low efficacy, the same should apply to their conclusion.

We also hear that we shouldn't take manufactured (i.e., "unnatural) drugs because big-pharma's just trying to sell you stuff to make money, then in the same breath they will try to sell you the latest all-natural (!) miracle cure...and not for free either!

To be sure, inconsistency doesn't mean the conclusion is false, it only means that the argument for the conclusion is poor and we need to either reject the premise(s) or the conclusion (or both) because both can't be true.  Sometimes people can hold the right views (conclusions) for the wrong reasons or as a matter of dumb luck, not because they arrived at them through good argument.

Unacceptable because of Begging the Question
The current use of "begging the question" meaning "raises the question" is something that irks philosophers to no end.  The original meaning of the phrase is "circular reasoning."  In other words, in your argument, you assume to be true the very thing you are trying to prove.

The classic example comes from an unsophisticated religious argument for the truth of the contents of the Bible.  A caricature of the argument goes like this:  How do you know what's in the Bible is true?  'Cuz it's the word of God.  How do you know it's the word of God? 'Cuz it says so in the Bible.

Notice that for the argument to work you have to assume the very thing the arguer tries to prove:  that the contents of the Bible are true.

Unacceptable because of Language Problems
We can call a premise unacceptable if it has one or more of the language problems we encountered on the section on definitions.  In other words, if the language of the premise is overly vague or suffers from semantic and/or syntactic ambiguity, we might say it's unacceptable (if context can't reasonably sort it out).

Suppose I claim that "I've never been seriously sick since I started taking Tibetan Booga-Booga Bush capsules.   We can't accept this claim because "seriously sick" is too vague.  For how long and for what intensity do I have to be sick to be "seriously sick".  Do I need to be hospitalized or just miss work?  Or maybe just miss my work out.   It's not clear from the phrase so we'd say the premise is questionable or unacceptable depending on the severity of the vagueness.