In my English class today, we were talking about thesis statements. One of the students said that one of the thesis statements didn't sound right; its syntax sounded odd. However, my teacher said that because he didn't show how to fix the error, that he has no right to criticize. Is this argument, that one must know how to solve a problem before they can ask about it, a logical fallacy or just a poor argument?
Is it a fallacy? Yes and no.
A fallacy is by most definitions a bad and persuasive form of argumentation, and to some extent, that is driven by context. In this case, the context of the argument dwells on the concept of rights. So, one has to address the question, what are a student's rights, and where do they come from? As a former teacher, I can vouch for the notion that in most learning environments, rights of students are heavily dependent upon the choice of teachers. So, within the context of your classroom, does a student have the right to criticize the use of syntax of another without the ability to articulate the problem and a solution? That is a function of the entirety of the rights and responsibilities that govern a student's conduct. These may extend beyond the choice of the teacher to those of the school and above to higher forms of social organization. The likely case is that if the teacher has a classroom policy of not criticizing unless capable of doing so under a set of conditions, then there is no fallacy because there is no argument. The teacher is merely citing a classroom rule. A fallacy must be a bad argument.
However, there is a second context that this scenario can be interpreted by, and that is an actual argument based, not on the rights of a student in a classroom, but the rights of someone in argumentation, typically exemplified by debate in various formats or along generally accepted principles of argumentation theory. Such a principle might be burden of proof. In this scenario, it seems likely that a teacher is committing what is known as an appeal to authority if the purpose of the conversation is to get to the truth or to learn collaboratively. In this case, if one proposes there is an error in syntax or semantics of a proposition, then one must at least describe the error and open the question to consideration. The truth of the proposition that another proposition is somehow flawed certainly doesn't require the correct formulation, although it would be persuasive to deliver.
Socrates: I have saw many Athenians in my day.
Plato: 'Saw' is not correct form of the verb.
Socrates: What's the correct answer in English? It's not my first language!
Plato: I'm not sure, but I'm fairly certain it is incorrect.
Socrates: You have no right to say I need correction if you cannot!
Plato: Based on what grounds?
Socrates: I'm the teacher!
Or better yet in a formal context:
Teacher: Pi is 3.0.
Student: Um, I'm sure that Pi is irrational and that's an approximation.
Teacher: Pi is not irrational! You are irrational! If Pi isn't 3.0, what is the value with certainty?
Student: Um, I'm not certain, really, but Pi is not 3.0.
Teacher: You have no right to criticize if you can't give me Pi to all of it's places.
The second one seems like a joke, but actually happened in a way. (See Indiana Pi Bill) In both of these scenarios, the invocation of "rights" is frequently a weasel word for asserting one's authority over the correctness in reasoning that good inference demands.
It sounds like it was an ad hominem fallacy where you attack the speaker instead of the argument. Here the teacher is attacking the speaker by saying "why should we listen to you if you don't have any better ideas?".
The only context I can think of in which the teacher's argument would have been valid is if the other student had explicitly claimed the existence of his better ideas (which he refused to state) as justification for the point he was making.
In this context (objecting to the syntax of a sentence) it seems to me particularly unreasonable to expect the critic to formulate an alternative. If a sentence has bad syntax it might not make sense at all so there might be no way to fix it.
It is perfectly possible to know that something is wrong ('sounds odd') without knowing what specifically and precisely is wrong about it.
For instance, you might be reading Lewis Carroll and see, recognise, that there is something wrong with the statement that the Cheshire Cat 'vanished quite slowly, beginning with the end of the tail, and ending with the grin, which remained some time after the rest of it had gone' (Alice in Wonderland, ch VI). Sure, it's possible for only the mouth to remain - but only the grin?
You know that something is wrong with the sentence (anyone going to challenge that something is wrong?) but you do not know, being unused to this kind of logical impossibility, that a grin is a feature (a configuration) of a feature (the mouth). If everything else has disappeared, there is no feature left for the grin to be a feature of.
It would be an umimpressive teacher who told you not to criticize Lewis' sentence because you don't know how to expose its error and reword the sentence in a suitable form - e.g. '... leaving only her mouth behind her'.
True, I have used a specimen of egregious nonsense to illustrate my claim: but the claim is correct. And unless the teacher can explain why someone, X, can't know-that without knowing-what, in the context of the thesis statements, then the tables are turned and s/he has no right to criticize X. To argue from (a) 'X does not know how to correct the sentence' to (b) 'X has no right to criticise the sentence' is fallacious, an error in reasoning. Extra premises might be inserted validly to connect (a) to (b) but currently they are missing and in their absence the argument is flawed by fallacy.