 The event by which the capacity to engage in vital activities is lost is one thing, and the state of affairs of its having been lost it is another. ‘Death’ can refer to either. However, the capacity to engage in vital activities may be lost gradually, rather than all at once, so it is reasonable to speak of a process of dying. In some cases that process is especially complicated, because the self-modifying activities of some organisms result in the construction of complex physiological systems that must remain largely intact for the self-modifying activities of these organisms to remain integrated. In defining death, some theorists focus on these systems, and claim that an organism’s life ends when that organism’s physiological systems can no longer function as an integrated whole, or when this loss becomes irreversible (Christopher Belshaw 2009; David DeGrazia 2014).