I recently defended my master thesis. One thing only went wrong: I said a certain method was rather new (which it was!) and the most senior professor in the room (my supervisor was not there, he had an unexpected meeting) contradicted me, telling me that it was old and had been done in the lab for ages. Honestly, I just gave in. He seemed so sure and I did not dare contradict him. However I was sure before and of course I have since checked, the method is indeed new, the professor was just plain wrong. What should I have done in the situation?
the most senior professor in the room contradicted me
This may happen due to any reason.
(my supervisor was not there, he had an unexpected meeting)
Probably, your supervisor was clear about his decision regarding you and the rest was just a formality (which actually happens in some cultures). So he chose to skip that ceremony (and attend that unexpected meeting) because he knew his decision would matter alone.
What should I have done in the situation?
Assuming that your supervisor had a green signal in his mind for you (which, of course, you can guess from the situation), you should have done nothing but tried to pass on with any reasonable negotiations.
Even if the above assumptions are wrong, you should have still done the same, because, considering your this statement:
I said a certain method was rather new (which it was!)
Especially, which it was! part, nothing can go wrong.
Of course, the reasonable negotiations would involve, you trying to defend that with solid arguments and references, while at the same time humble enough to listen to his criticism and show respect to get along.
Did you pass your thesis defense? If so, it's all water under the bridge.
If it is eating you up inside, you could send a polite note to the senior professor (cc:ing your advisor) thanking them for the question and that now that you've had a chance to re-check things, that you are ever more certain that your method is different from the suggested prior method because of x, y, and z; but perhaps you misunderstood his question and there was another earlier method he was referring to, and if so -- could he please send the reference? (tip of the hat to @gnometorule)
If you go this route, I would frame it as a letter of thanks, appreciation, scholarly inquiry, and to keep the tone as non-accusatory as possible. As @guifa notes, some
jerks professors view thesis defenses as a type of hazing -- a no-holds-barred opportunity to test your mettle; and what happens in defense should stay in defense. You do not want to drag this out. It can easily blow back in your face or the face of your advisor if the senior faculty member has a thin skin (which unfortunately many academics seem to have).
Again, if you have your Masters, then I would just be happy with that and just make rude gestures towards that senior faculty member from the safety and privacy of your own home. And don't ever do this when you become that person in a position of power.
You changed the question slightly from the initial posting from [what to do after the fact] to [what you should have done at the moment]. As note above, all questions at thesis defenses are fair -- even ones that are built on false or falsified premises. It is, after all, a "defense" and as a scientist you should be able to defend yourself from both truthful and false/falsified statements without having to resort to ad hominem counter-attacks. You respond based on your training and experience what you believe to be correct. And obviously given that you passed the defense, the examiners thought that you gave satisfactory responses on the whole. As Queen Elsa teaches us, let it go.
Generally, when faced with questions or comments like this one, you need to respond in a way that is open to the possibility that the professor is right, but that nonetheless demonstrates your belief in your own position. Don't give ground too easily, but don't get too entrenched either, since you need to be open to new information.
How you do this depends on how specific the professor's comment is:
If it was just a vague contradiction - "That's not new, it's been around for ages" - then you need to probe for more information. "That's interesting, I've not come across any previous use of this method - could you tell me more about where it's been used?".
If prof responds in detail ("It was done by Professor X in paper Y") and paper Y is not one you've come across, then your response is similar. "That's really interesting, I will look into that. Perhaps we can discuss this further after the talk." Or you might be able to second-guess the method used even if you don't know paper Y. "If they used method Z, then it's related, but our is different because..."
If paper Y is one that you are familiar with, then you have something concrete you can discuss. "That's certainly an important method, and provided inspiration for our work [if it did], but I referred to our method as new because it has these important advances/differences..."
However rude the professor is with their comment, it may still be a valid point, so try not to take it personally. Ignore the tone and just respond to the substance as politely and scientifically as you can.
Finally, it's easy to say all this in hindsight, but when it's early in your career and you're faced with an imposing figure contradicting you, it is only natural to give ground under pressure, and the fact that you successfully defended your thesis shows that you coped well with the overall situation!
Option A - Argue about it in front of an audience and focus attention away from your real presentation. Focusing on proving the senior professor wrong in front of an audience is not going get you anywhere.
Option B - Let it go. Go research it again thoroughly on your own. If you think it's a new approach, gather your research papers that support your claim. After you do your specific research, kindly ask the senior professor for examples of clarity on his comment. (Don't go in his office and slam a paper in his face proving he is wrong.) Go see him in person. Don't send an email because emails have no vocal tone to them.
Overall, I bet that it is not a 100% black or white issue. Perhaps the professor or you are thinking of a "similar" method or a method that goes under a different name. You may call it binary and he calls it base-2.
It's no big deal. Some people just like to speak up and make comments no matter what the situation. The senior professor probably won't even remember what he said after one week. Nevertheless, it is a good learning experience. You get to practice how to deal with confrontations that you were not prepared for.
People (including professors) make mistakes. I have been mistaken myself in similar situations as you described, and would not attribute any kind of malice to the professor's remark during your defense. As @RoboKaren pointed out, you got your degree, and it is mostly water under the bridge now.
In case it irks you a lot, I would recommend not to send an email to the professor, but to talk to him personally, maybe phrasing it as a misunderstanding regarding the scope of the method. An email might come off as somewhat aggressive.
Two actions should be taken:
A- Forget about it. Say Thank You and move on during the meeting.
B- Make very well sure that you're right and he's wrong before just assuming you're right. I've seen (and refereed) many cases where someone just knows something is novel when its not. This can happen for many reasons. Keep in mind that this person has been around longer than you have, may well have a wider understanding of the literature than you have, or have an inkling that something that has historically been presented in a slightly different way is exactly what you're talking about but is a little difficult to make the jump.
"Honestly, I just gave in. He seemed so sure and I did not dare contradict him."
You have answered your own question - you shouldn't have done this. If you were sure of yourself and your facts then you wouldn't have given in and you would have contradicted him. You are allowed to disagree with "senior professors" - they make mistakes too. That you did not suggests to me that you weren't sure of yourself or the facts.
Part of these occasions is to test whether you have the self-confidence to know your discipline, know when you are right and to argue your case.
Of course, if you were wrong...
When people disagree about facts, the only useful procedure to solve the disagreement is to appeal to an outside source that is accepted by both parties.
Typically this is not feasible to do in the middle of a presentation, either because such an accepted outside source is not available, or even if it was (say through an internet connection that is active on the spot), it will take away time that is scheduled otherwise. To the degree therefore that rebutting the claim is not essential and/or critical for the purpose at hand, you, as the presenter (and so the one with the higher stakes in the situation), should wisely let it pass.
But it would be a peaceful way to go about the world if you contacted the other party afterwards, by say, an e-mail that would supplant the necessary information about the matter. It is not about you triumphing over him or truth triumphing over falsehood, -it is about helping another person to not make the same mistake again.
While I believe user2390246's answer should be the preferred way to handle this kind of situation, I think the safest path would be to acknowledge the contradiction and quickly move on.
That's interesting, I've not come across any previous use of this method, but I'd love to know more. Could we discuss this afterwards?
If they decide to press the issue, user2390246's answer has the details how to handle that, but I'd be willing to bet they won't.
If they agree, then obviously do approach the professor sometime later (preferably in person, during their office hours, after double checking your facts).
It should be noted that this only works if the method isn't central to your thesis and the contradiction doesn't directly threaten the validity of your results. If that is the case, then you have no choice but to push back.
This was your defense. You should expect senior faculty to give you challenges and questions like this, because they want to test the limits of your knowledge and usually won't be satisfied until they've gone beyond them. How far can they go before they reach "I don't know?" When you get there, do you have what sounds like a reasonable strategy for how you would find out or resolve a question?
When you get a challenging question like that, the first thing to do is listen and make sure you really understand what the question is asking. Reflect it back to the asker to be sure and to demonstrate you've got it. Then, figure out if the challenge/question is something that is core to your thesis, or a side/auxiliary point. If your main claimed contribution is this allegedly novel method, and the method not being novel would mean you don't have a contribution left, that's a core issue. If you just used the method and the results of it are what's important, and you only mentioned in passing that the method is relatively new, then it doesn't matter so much. Consider saying what you know and offering to continue the conversation "offline" or afterward, when you can find out more details about the citation. With other sorts of non-core questions e.g. about your method or result you can use a response like "I'll have to look that up and get back to you on that." This helps keep the conversation focused on the core elements of your thesis.
More important for the defense, consider and respond to how it would affect your work if the questioner's point is accurate.
As far as what I found < maybe add, and this is what I did to look >, I believe the method is relatively new. If it's actually been used for a while, that increases my confidence in the reliability of the results it produces and could help make the conclusions even stronger. Thank you for letting me know about this and I'd be glad to continue the conversation afterward to discuss more details."
If he takes you up on the offer to get more details, try to get pointers to authors or papers where you can check. Claims of novelty are much easier to disprove than to support, conclusively. You may still be right, but you're not going to prove that in the moment of the defense presentation nor do you necessarily need to. You need to show how you respond to this potential new information and what knowledge you assert in your response, including some analysis of how that (counterfactual or not) would affect your thesis.
Finally, if you already passed the defense, you can just view the professor's challenge as part of the challenge of a defense, and congratulations on having passed through that process successfully.