Life: An Ill-Defined Relationship

For the most part of the history of humanity, the definition of life has not been an overwhelmingly important issue. Or at least, it was not a controversial issue. It was sufficient to go by a simple rule: you know it when you see it. Questions like whether viruses are alive or why a brain-dead person is pronounced dead, although her heart works, do not have a long trajectory in the history of understanding life. However, progress in science and technology continues to complicate the issue. What does life mean when we talk about synthetic biology, artificial bacteria, prosthetic genomes, bionics and robotics? How can we know what we are looking for when we search for life in the universe, if we do not have a clear definition? How big a problem is this? Until now, all suggested definitions of life have been falsified by counter-examples. Signs like metabolism, growth, reproduction, reaction to external stimuli, adaptation to changes in the environment, some form of communication that leads to some form of coordination - none of these provide an irrefutable definition of life, since these traits can be found in various types of systems, some of which cannot be named life by any other criteria.