Life = energy/mass = 1
L = mc2/e = 1
Life exists when the energy of an object is in equal proportion to its mass traveling at the speed of light squared.
Update 18.12.2010:
As with the following post, I now believe that this statement is in need of revision. This ratio does not reflect the existence/non-existence of life, but rather the ratio at which a higher level of complexity in terms of chemical evolution occurs.