Why Time Travellers (Still) Cannot Change the Past
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In an earlier paper I argued that time travellers cannot
change the past: alleged models of changing the past either
fall into contradiction or else involve avoiding, not
changing, the past.  Goddu has responded to my argument,
maintaining that his hypertime model involves time
travellers changing (not avoiding) the past.  In the present
paper I first discuss what would be required to substantiate
the claim that a given model involves changing rather than
avoiding the past.  I then consider Goddu's hypertime model
and an earlier model due to Meiland.  I argue that neither
author does what would be required to substantiate the claim
that the model involves changing (not avoiding) the past.  I
go on to give reasons for the stronger claim that no-one can
present a coherent model and also substantiate the claim
that it involves changing (not avoiding) the past.