Good point, as there's even competition going on amongst ideas... 'survival of the fittest' also I guess. The Bible as idea has been quite successful at this, but I doubt it's because of it's message.
but I dont agree with the idea that we should tolerate ideologies simply because they have survived for thousands of years.
Interesting point, as this is often exactly what seems to be happening with a lot of religious ideas. Simply because they are 'old', they get a special kind of attention or treatment... Can't say that itself is a bad thing, as we should all learn from our history, but still.
Biology's idea of species usefulness, and it seems to be your idea also, is that it somehow contributes to the ecosystem. However not all species are useful by that definition. Many, as a matter of fact, are anti-useful.
I don't think it makes much sense to make a distinction based on 'usefulness' within an ecosystem. There aren't many ecosystems in which a certain species is active but sort of outside of it's 'circle of life'. I mean, is there any ecosystem in which there's just one animal? Probably not as it would be out of balance.
The mere fact that a certain animal, bug or whatever can be eaten by others gives it a certain kind of 'usefulness', but I agree with you on the 'vacuum' word thing.
Cheers
