(Some) opinions are worthless

I once took a class that compared evidence in a court of law vs evidence in other disciplines.  According to the ideal, the lawyers present facts to the jury, and the jury makes inferences based on those facts.  But there are some kinds of inferences that the jury can't make on its own.  For this, we need the witness to give an "opinion".  It may be something as simple as the opinion that a noise sounded like a gunshot.  Or it may be an expert opinion, which is an inference that is too difficult for the typical juror.

Of course, I've probably got the description completely wrong somehow, and courts probably don't match the ideal.  But it doesn't matter, because I'm really talking about blogging, not the law.

Whenever I blog an opinion, I have to think about what I'm doing.  Have I presented new evidence for this opinion?  Have I presented new arguments that you couldn't have thought of yourself?  Or am I just trying to persuade by sheer force of personality?

Let's take a short case study, dug from my blog archives.  Back in February, I posted a video of a panel of atheist men discussing sexism.  Some people thought the panel was no big deal, and others thought the panel was terrible.  My comment on it was brief:

I don't think I have anything especially insightful or persuasive to say about this, but I will express my opinion that the whole panel was deeply disturbing.

I was not stating a new position.  I was not presenting a new argument or new evidence.  I was merely saying which side I was on, namely the side that thought the panel was terrible.  Nobody should find this persuasive, just because some random guy on the internet said it.  So what was the point?

In this case, the point was to provide evidence for a different claim, one that was unstated.  I was claiming that some skeptical men are concerned about sexism, since I myself am one such person.

But suppose I had said something similar about UFOs:

I don't think I have anything especially insightful or persuasive to say about this, but I will express my opinion that UFOs are Unidentified Flying Objects, and not Alien-Identified Flying Objects.

That would be a worthless opinion, because it's not a novel position, and has no new supporting arguments or evidence.  Perhaps I would persuade people anyway if I stated my opinion in an especially succinct way, or if (hypothetically) I were a widely respected blogger.  But you, dear reader, should see through it.