At a recent faculty meeting, as my attention drifted just a tiny bit at one point, I decided that the faculty evenly divides into optimists and pessimists, and that this classification scheme is nearly perfect -- far better than grouping the faculty by related research disciplines, age, gender, geographic origin etc. The only thing that keeps my classification scheme from being completely perfect is the existence of a colleague who will take a contrary stance just for the sake of being contrary (or for prolonging the enriching faculty meeting experience?).
In the specific context of faculty meetings and administrative issues, I am an optimist. The pessimists have a useful purpose, but mostly they are annoying, particularly in long meetings. I readily admit that optimists can be annoying as well, but at least we want to get things done instead of listing all the reasons why we shouldn't do anything except maybe sit in a conference room and talk for hours.
When my daughter was younger, we made up a game called optimist-pessimist. I would say something like "It's raining. There will probably be thunder and lightning and strong winds that will destroy flowers and scare the bunnies", or "It's raining. I bet there will be a rainbow, and birds will come out and splash in the puddles" and then she would say "optimist" or "pessimist". It was a stupid game, but it's amazing what entertains a 3 year old. Although we didn't delve into the wonderful world of department administration for examples, I bet she could have correctly guessed the label to statements such as "Let's not talk to people in that other department because they won't be interested in anything we are doing."
I don't always do well in debates with my pessimistic elders (the senior senior professors) because they like to frame the discussion in terms of their superior knowledge acquired over their many years in academia, whereas I, a junior senior professor, am naive. Perhaps there is a fine line between being optimistic and being naive, but mostly I think they are trying to undermine my arguments with contentless blather. I could do without that.
An entire department full of optimists might be a bit terrifying, though.