 My current measure of existence is relevant only for gedanken situations like Wigner’s friend Wigner 1961 (recently revived by Frauchiger and Renner 2018) which demonstrates the meaning of the measure of existence of a world as a measure of its ability to interfere with other worlds. If I am a friend of Wigner, a gedanken superpower who can perform interference experiments with macroscopic objects like people, and I perform an experiment with two outcomes A and B such that two worlds will be created with different measures of existence, say \(2\mu_{A}= \mu_{B}\), then there is a difference between Lev A and Lev B in how Wigner can affect their future through the interference of worlds. Both Lev A and Lev B consider performing a new experiment with the same device. Wigner can interfere the worlds in such a way that Lev A (the one with a smaller measure of existence) will not have the future with result A of the second experiment. However, Wigner cannot prevent the future result A from Lev B, see Vaidman 1998 (p. 256).