cj- Scepticism (I stick to the British spelling) is a simple process; the attitude that acceptance follows observation of the evidence.
We are all sceptical about some things- door-to-door salesmen, government statistics, whatever.
In the specific area of the paranormal , which is what this board is about, scepticism is exactly the same process we all apply every day.
However, we must also remember that any process applied over time accumulates data and those data show patterns.
The reason we are sceptical of government statistics is because , historically, they have been massaged to demonstrate what the party in power wanted us to think.
The reason we, as sceptics of the paranormal have what you may see as an a priori scepticism - often labelled a closed mind- is that when we study the data , collected over centuries, we observe a miserable pattern of non-event, human credulity and deception.
Had you made this criticism in 1600, I would have sided with you. The data were not in. But this is 2007 (or soon will be). The data, very largely are in. The laws of physics are much clearer now than then. Some things can be ruled out a priori, because the situation is not one of a blank slate.
There are things we know, which rule out other possibilities, among them perpetual motion and free energy.I may need to examine a perpetual motion machine in detail to know why it will not work, but I do not need to wonder whether it will work. It will not. This is not an a priori assumption. It is as hard a fact as any in existence.
Some possibilities persist. There may well be an unidentified animal in Loch Ness. There is nothing impossible about that. The probability of a Jurassic marine reptile being there, 9000 years after the Loch Lomond Stadial is slim to the point of unbelievability. Of course I cannot dismiss it 100% as I can the PMM, but I can confidently assign it a very low probability.
I have sometimes been offended by accusations of closed mindedness on some paranormal issues, from people who were profoundly ignorant of the reasons for my scepticism and who, seeing no good reason not to believe themselves, simply supposed I had none either.
I do not think I am closed minded to possibilities.
I think I filter probabilities through a screen of established facts.
There is a great difference.