Be very clear about exactly what the author is claiming. (Avoid direct quotes, and make sure you phrase the claim accurately.)
Here are some common mistakes to watch out for when evaluating assumptions:
It is a mistake to say that the assumption fails because there is no evidence. Lack of evidence is part of the definition of an assumption. (An assumption is a claim that the author does not try to prove. Evidence is proof.) If an assumption is wrong because there is no evidence, that is the same as saying all assumptions are wrong. Obviously this cannot be true.
The point of evaluating assumptions is to figure out whether they could be proven, not to say they have not been proven. You must decide if the claim is one that you, or the author, could prove if they tried. This means thinking about what you know or believe about the topic and judging the claim on that basis.
Again, simply pointing out the lack of evidence does not disprove the claim. It simply shows that an assumption is being made. It does not say whether the claim is true or not.
If your paper says something like, "This assumption is bad/false/invalid because there is no evidence to support it," the paper has failed to evaluate the assumption. All it has done is say that there is an assumption, and then made the mistake of implying that all assumptions are bad by definition.
Many people believe that all assumptions are bad, because you must prove every claim in your argument. This, however, is a logical impossibility. For example, suppose I want to prove that it is raining. I point to the drops coming from the sky. That is my evidence. But I must assume that the drops have no other source, that they are actually water, and so on. At the most basic level I must assume that my eyes and my sense of touch are giving me an accurate picture of reality. No matter how much you prove, there is always something more basic that you take for granted and do not try to prove.
This is the opposite of mistake number 1. If an assumption is a claim that the author does not try to prove, there cannot be any evidence for it. If there is evidence, the author did try to prove the claim, so it is not an assumption.
If your paper says something like "The article provides support for this assumption," or "The authors give evidence that this assumption is true," it is making a basic mistake about the meaning of the word "assumption." The claim your paper has identified is not an assumption.
Once again, the idea is to spot a claim that is not supported by evidence in the article, and then decide whether it could be supported, based on what you know or believe about the subject. You must use your own judgement in deciding this. You cannot base it on what is in the article. The whole point of this kind of analysis is to spot the points where the article does not support its claims.
This is another variation on #1 and #2: confusion about the meaning of "assumption." If the author does a bad job of proving the claim--for example, by giving irrelevant or unrepresentative evidence--then the claim is not an assumption, because an assumption is a claim the author does not even try to prove. Trying and failing is not the same as not even trying.
This is an example of what’s called “circular reasoning,” or using the claim to prove itself. Let's say the article assumes that investing in renewable energy will boost the economy. Suppose your paper says something like this: "I agree with this assumption because if we spend more money on wind and solar, it will be good for the economy." This states the claim in different words, but it does not explain why you think it is true. To do that, you must add information to the claim (provide your own examples or other evidence, or explain your reasons). Simply re-stating the claim is not the same as supporting it.
This is the mirror image of mistake #4, and is faulty for the same reason. Here, too, you must say why you think the assumption is untrue, giving your reasons (explain your thinking and/or give evidence to support it).
If we cannot know, there is no basis for agreeing or disagreeing. Generally, however, even if we cannot know for sure, we can certainly make an educated guess. Your job is to make that guess, and explain your reasons. It may not be perfectknowledge rarely isbut it is better than nothing.
If you really can’t say whether an assumption is true or not, you can at least say whether it is reasonable. In other words, can you see how someone might think this, even if you yourself can't say for sure whether it is true?
Watch out for absolute statements (saying "all" or "none," "always" or "never," when what you really mean is "some" or "few," "often" or "rarely.")
This brings out a more general point about arguments that may seem paradoxical (contradictory): Sometimes, the weaker claim is the stronger claim.
I phrased this in a contradictory way to get your attention, but really I’m cheating because I’m using two different meanings of “strong" and “weak.” Here’s what I mean:
This illustrates the importance of what are called “qualifiers.” These are terms that change your statements from absolutes into partial statements, or certainties into possibilities. For example:
Some students believe that such qualifiers make their claims less convincing. Often, however, they actually make the claim more convincing because they leave room for exceptions. They state a general pattern without claiming the pattern is universal.
To use a structural analogy: Sometimes the structure that can bend is stronger than the one that can’t.