What about Virii and prions? Virii work by taking over a cellular host, by directly altering some physical structure. This process require energy... and meets all the other criterion of life. > > > > > > Further, there is nothing I've read to counter the idea that virii didn't evolve from a more complex form... meaning that under this definition life can become animate nonlife--creating a category we've never dealt with hI. > > > > Virii are parasitic, alive but not independent at any time. Other living parasites were initially independent. As such I would classify virii as not complete life under proper definition. > > Well, if there was a "proper" definition, Tony's site wouldn't exist!-You are right. I couldn't think of another way of putting it. Life is still not properly defined, but I consider independence part of the definition