 However, there are clearly cases in which (EDR) fails to capture the intuitive sense of dependence at hand. Consider a living organism. A living organism would appear to depend for its existence upon its parts, such as cells. But we also know that a living organism may survive a change of any of its cells, provided that the change is effected in a non-disruptive manner. It is true, of course, that such an organism must have parts such as cells if it is to exist, but which objects those parts are is inessential—and consequently it is not the case that it depends for its existence, in the sense defined by (EDR), upon any one of those parts. But it is possible to define another sense of existential dependence in which it is true to say that a composite object depends for its existence upon its proper parts; a generic notion of existential dependence, defined as follows: