Considering that there is no proof Roy Emerson is a tennis expert and that probably most posters on MTF are not tennis experts, my opinion is that his opinion is irrelevant.
Irrelevant to you, only, not irrelevant tout court
. Imagine a guy coming into a discussion about which he knows nothing. "Any proven experts here", he asks. "No", they reply. He lets them continue on. That's the extent of your contribution to the debate.
Imagine you're one of the people debating. Suddenly the guy says, "Hey you! Your opinion is irrelevant!". How do you think you would take that? You're having a discussion about something which, lets say you have expertise in, and someone else (who has no expertise) tells your opinion doesn't matter. He doesn't say, "hey this doesn't matter to me
", because then the 'argument' would end right there.
That's you in this debate. This 'debate' has gone on for so long because nobody realized you have no positive arguments (about the topic) to make! You're not participating in anything, you're standing on the sidelines asking people to show their expert credentials, because you believe you're incapable of evaluating arguments on their own merit.
I asked this question because it is part of my argument.
What argument? As you said yourself, you're not making any "positive claim[s]". And as such, no one has to prove their expertise to you. It is rude to ask for such proof as a matter of entitlement.
It's possible that some posters can prove that they are widely recognized as tennis experts.
I'll repeat what I said again:
"I think it is also very strange to go to a site, and expect a response that will be impossible for the majority of members to give. Maybe it would help if you asked nicely, rather than dismissing peoples' opinions as irrelevant."
If you want expert opinions, an anonymous site like this is the last
place to go.
This is my revised argument.
Pete Sampras has high level practical understanding of tennis. A "tennis predictor" is someone who has a good understanding of past statistical trends, and the ability to take into account unknown variables. The best evidence of this ability is a successful track record of past predictions. From the fact that Pete Sampras has a high level practical understanding of tennis it does not follow that he is a tennis predictor.
Note: I am not saying Sampras is not a "tennis predictor"; I am saying we cannot infer this from his "high level practical understanding of tennis".