  Like many basic concepts, it is difficult to non-controversially define life. Most people simply avoid the issue by ignoring marginal cases, accepting the vagueness of the boundary cases, or setting aside the whole issue as beyond their scope. Nonetheless, there are many people whose work seems to require a rigorous demarcation of life, especially in new scientific contexts, such as astrobiology, origins of life, or synthetic biology. As such, the nature of life continues to be a hotly debated topic.