***The first truth is that we often make mistakes even when we fully understand what we are talking about. Can you imagine how many mistakes we make when we are not entirely familiar with the subject?***
Yes and no. True, we are liable to go off tangent without facts that we are unaware of (e.g., Dick has no knowledge of Frege and his failures, so of course he isn't privy to seeing Frege's errors). On the other hand, no one on earth is an expert in every field. That is why wide debate is so important in the discussion of issues. If I make a mistake, you might catch it, or Dick might catch it, and so on. The other reason that we shouldn't be intimidated in tackling such topics as more or less amateurs is that often philosophical issues can be tackled best with common sense. For example, there are many metaphysical philosophers who tackle the kind of mind games that Alan ventures, but wouldn't such deep knowledge of philosophical issues be better applied with common sense as your basis? I think we know it is against common sense for there to exist a '4' out there in some Platonic realm, yet this is what many Platonic philosophers believe. Having a good sense of what makes sense is often the best guy to approach philosophical issues.
***The second truth is that, no matter how you look at it, truth (ipsi-duda) exists. Now you, Dick, and a few others are willing to maintain that the concept of truth is not important. While I can't possibly deny your right to assert that, I reserve the right to think that, if truth is not important, then nothing you say is important.***
I think the concept of truth (ipsi-duda) is important to humans. The question is does our concept of truth approach the truth that may or may not regulate the fundamental structures of the universe? I am very much doubtful that it does. First off, it remains a definition problem of deep debate in philosophy, and it does not appear likely that we will ever agree on what truth is exactly. The topic of truth appears, to me, to be situational based on the actual context that we are discussing. In some cases truth is pragmatic based, in some case truth is correspondence with the facts, in some cases it is coherent with other facts and theories, etc. It might be that truth is like snow, there are many different kinds of snow at different locations and altitudes throughout the world, and humans simply label it 'snow'. As far as we know, there are infinite varieties of truth.
Our main task is to settle on conventions of truth that enable us to deal practically with issues. Beyond that, we are engaging in a grander goal of finding deeper, if not ultimate, meaning in the world. That's of course desirable, but we have to accept our limitations in achieving any certain success.