In this essay I defend the claim that the life of a living being is not one of its properties but something different: a mode of being. It follows from this that living beings should not be taken to be things that possess the property of being alive. Second, I argue that living beings are essentially involved in ongoing activities as long as they exist. Life cannot only be a disposition to be active, but must itself be an ongoing activity. Third, I suggest that for something to be a living being is to engage in activities whose success is determined by criteria that emerge exclusively from a proper account of the nature of the living being in question. To identify something as a living being is not to attribute a particular property to it, but to say what criteria apply to what it actually is or does.