pz

I know you don't think that way anymore, but that is kind of pathetic logic. Then how do you know that homosexuals aren't innocents who are suffering for the sin of some guy the loving god decided to zap with some horrendous plague because, maybe, he mowed his lawn on the sabbath? This view of the punishments for sin being visited on the innocent as a kind of collateral damage would make me wonder who god thinks he is -- George W. Bush?

Gurdur

Yes, but so what ?
"Life" and "living" are useful concepts, slowcoach, so it makes sense to use them --- and arbitrarily defining viruses as alive, as you do, makes no sense either.
Why not simply leave them in the gray zone too ?

scigirl

Ha ha! I'm stealing this quote from you!

I always wondered why God hated little babies in Africa so much - cholera, rotavirus, now HIV. Jesus loves the little children? Perhaps not...

scigirl

Doubting Didymus

Because they eat people from the inside out, mainly.

Seriously, I do place viruses in the 'grey zone'. That's the whole point of a grey zone! Further into the 'white' are bacteria, still further are simple multicellular organisms and so on. The very fact that I think a broad grey area exists means that I DON'T arbitrarily define this as alive and that as not. There are simply varying degrees of 'living', rather than an on/off switch: viruses are low on the scale, eukaryotes are higher and prions are lower.

liquid

Hello to those of you who remember me - just had another chance to get on the net so thought I'd pop by to refresh my account and shoot of a post or two! Back properly in summer....

The true status of the concept of 'life' is that we don't really know what it is. Life to non-life, based on known properties, is a fairly continuous scale, as evidenced by by similarities exhibited in the organic chemistry to prion to virii to viroids to prokaryote to eukaryote to multicellular organisms.

An analogy I like is that of the bald man. A man with no hair is bald. So what is a man with one hair? No-one would say he is not bald... two hairs? five? ten? a hundred? probably still bald... a thousand? two? ten?

The point is that there is indeed a grey area in the concept, and although this is not a problem in normal conversation, it can be a problem in certain scientific communication. So arbitrary (but this does not imply invalid!) criteria can be made. In a hair regrowth study, we might make a quantitative definition of baldness at less than 20 cm^2 hair cover on the head.

In biology, we get many similarly concepts of life. There is the old 'characteristics' definition we are taught at primary school - that a living organism respires, grows, senses, reproduces etc. There is the cybernetic definition (iirc) which is "A network of inferior negative feedbacks subordinated to a superior
positive feedback.". Check out the Brandeis consensus here for another. Or there is the thermodynamic definition. The list goes on.

Indeed, you even get religious definitions of life! For instance, a living creature is that which possesses a soul. No idea how you measure that one!

You see the same thing crop up all over biology - take the multiple definitions of species as one of the most famous.

All these definitions, and more, have their uses and their individual merits. You will find biologists (and philosophers, computer scientists, chemists!) arguing for each. But no single one has given an overarching insight because.. well, who knows? It might truly be a continuum. There may be some property of life we have yet to recognise. Or it may be no more than a human-invented whimsy of an idea!

Doubting Didymus

Excellent post, liquid.

Xeluan

Evidence had emerged that SARS jumped from animals to humans.