Truth and Acceptability
When evaluating an argument internally, there are two questions we ask:
- Are the premises true?
- Do the premises give support to the conclusion?
Previously, we have covered the second question, and found out that an argument can give strong or complete support to its conclusion even if the premises aren’t true. Of course, true premises are important for a good argument also, so today we take a look at the first question.
Previously we defined truth as follows:
Truth is a property of statements. A statement is true if the world actually is how the statement claims it is. It does not make sense to call an argument true.
We are going to be looking at a more broad concept than truth to start off with: acceptability. You may be wondering why they are different concepts at all. Surely for a premise to be rationally acceptable all it needs is to be true, right? This is a very plausible notion but the reality is a little more complicated.
Logic itself does not deal with finding truth (that’s what we have other branches of epistemology for!), logic is concerned with preserving truth. What I mean by this is that if we are given true premises, logic will show us what follows from them and what doesn’t, essentially preserving the truth of the premises until it gets to the conclusion. We have been focusing on more practical techniques than formal logic, so we need to find grounds for acceptability of premises too.
Sometimes we create arguments from premises we suspect or know to be false, in order to investigate their consequences. This is one example of how an acceptable premise may differ from a true one. Also, you may be trying to convince someone of a particular conclusion but they do not agree with one of your premises, although it may be true. Using this premise in order to convince them would certainly not be acceptable, even though it may be true. Remember, arguments are used for a purpose, and an argument that does not fulfil its purpose because it uses true yet unacceptable premises can scarcely be called a good argument.
So if acceptable premises are not simply true ones, what makes a premise acceptable? The answer is not simple; there are a variety of factors that come into play. In general terms, a premise is acceptable if it is rationally believable. There have been many cases of widespread belief in something that has turned out to be false (Earth at the centre of the universe for example). These types of premises would be considered acceptable until their error was uncovered. ‘Common beliefs’ is a phrase that captures this type of thing well, although we must be careful to make sure that our arguments’ intended audience shares those beliefs. I could make a statement about something well-known in Australian culture, and it may be an acceptable premise here in Australia, but elsewhere it may not be. Premises can change between being acceptable or not, but they cannot change between being true or not. It may also be the case that two experts in a field are debating a point, and the premises they are using are facts unknown to everyone outside their field. These would also be acceptable because of the intended audience. Context is a vital consideration in judgement of acceptability.
There is a problem with the above approach. If I were in a debate with someone and they were telling me that the Earth was not flat, yet I rejected this premise because I did not know it to be true, could it not be argued that I ought to know that it is true? In these cases, a notion of ‘widely held belief’ is useful as there is a certain amount of belief that one can be expected to have about certain topics, particularly if they are engaging in arguments about the topic. You can probably see that these notions are not particularly rigid or easy to define, but I hope you can see the types of general conditions that we look for in acceptable premises.
There are of course other types of premises that we can deep acceptable. Premises that are supported by a good sub-argument for instance (which itself had acceptable premises) would be acceptable, whether that is done in situ or somewhere else. When reading academic literature many premises from other authors are used and the sources are detailed in the footnotes for instance. Testimony from reliable sources could also be deemed acceptable, providing that they are asserting something plausible and they are making assertions in an area that does not go beyond the experience and competence of the person who is making the claim. Claims that experts make about their field of expertise are also acceptable premises. If a trained medical specialist diagnoses us with something, then it can hardly be called rational to deny their claim without any training in the area ourselves.
Another type of premise that we can deem acceptable is an obvious a priori truth. An a priori truth is one that we can know to be true without having to look at the world. These are similar to necessary truths which we have talked about earlier, and can be thought of as the same thing for our purposes. An example of an a priori truth is “kittens are young cats”. We do not need to find a kitten and find a cat and do a DNA comparison to establish that kittens are indeed young cats; we know that the statement is true because a young cat is the definition of kitten. This is in contrast to a posteriori truths, or contingent truths, which are truths that we have to look at world to discover them rather than know them purely by definition. An example of an a posteriori truth is “kittens are cute”. The same terms; a priori and a posteriori can also apply to falsehoods with the same conditions.
Provisional premises are statements you assume to be true so that you can see what the logical consequences will be. You can do this even if you do not believe, or are unsure, that the premises are actually true.
The judgement of premises as acceptable or not is a tough process to formalize. I hope I have given you a decent overview of how judgements should be carried out. Remember a few key guidelines..
- Premises are not acceptable if your audience is not likely to believe them; unless
- The premise can be considered ‘widely held belief’, and it is a rational expectation that your audience should hold that belief.
- Obvious a priori truths are acceptable.
- Testimony from a reliable witness and statements from experts are generally acceptable.
- Premises that beg the question, regardless of their truth, are not acceptable.
- Premises may be accepted provisionally to see what the consequences are.
When trying to convince someone of a conclusion, you must start with premises that they accept. One specific type of unacceptable premise was introduced very briefly in a previous article: begging the question. Begging the question is when you assume the conclusion of an argument in its premises. Premises that do this are unacceptable even if the audience agrees that they are true, because it means the argument is not actually proving anything at all. This is actually a very common problem and will be covered in more detail in future articles.
Premises that are unacceptable are simply those that do not fit the criteria, but I will cover a few more specifics. Claims that are easily refutable are obviously not acceptable. For instance, if someone were to make a general claim and there were obvious counter-examples, that claim would not be an acceptable premise. Claims that are a priori false are not acceptable, and neither are premises that are not consistent with each other within an argument. Vague or ambiguous premises can also be rejected, even if they are true, because argument often relies on the details, and making mistakes about the details of something due to a vague or ambiguous statement is something to be avoided. Highly controversial premises may also not be acceptable, or at least require further support to become acceptable.