 A second set of problems stems from an indeterminacy of meaning in the test, not from difficulties of factual verification. There is a great vagueness in counterfactual judgments. The vagueness lies in specifying the possible world in which we are to test the counterfactual (Cole 1964a,b; Lewis 1973b). Suppose a defendant negligently destroyed a life preserver and a sailor drowns for want of one. When we say “But for the defendant’s act of destroying the life preserver”, what world are we imagining? We know we are to eliminate the defendant’s act, but what are we to replace it with? A life preserver that was, alternatively, destroyed by the heavy seas? A defendant who didn’t destroy the life preserver because she had already pushed the victim overboard when no one else was around to throw the life preserver to the victim? And so on and so on. To make the counterfactual test determinate enough to yield one answer rather than another, we have to assume that those applying this test share an ability to specify some definite possible world that is “similar” to our actual world save that in that world the defendant did not do what she did in the actual world.