This might be thought to rule out the appeal in the previous paragraph to possibilities where Sonia never uttered string S in the first place, for those possibilities presumably differ from the actual world at parts of spacetime other than the local area of the utterance. Sonya's intentions when entering the time machine, for example, may be different in the world where she utters S than they are in the actual world. But this principle has no plausibility. No one supposes that the result of patching together physically possible partial configurations of the world need always result in a physically possible total configuration. Clearly, neither interpretation is what Deutsch and Lockwood had in mind by the principle of autonomy.
Autonomy is a logical property that is highly desirable for the laws of physics to possess.
The idea, pretty clearly, is that the ability of humans to affect their local surroundings is in some sense independent of what goes on in remote parts of the universe. The principle thus interpreted needs certain qualifications. Brainwashing, injury, technological limitations, etc. set boundaries on what physically possible configurations we can bring about. The assertions that Tim can't, and that Tim can kill Grandfather are compatible, because the relevant facts in each case are different. S. Thus, if some solution like Lewis's adequately dissolves the Grandfather paradox, we have been given no motivation to consider the more exotic interpretations of quantum mechanics to which Deutsch and Lockwood appeal.