"Tamberly had proposed taking Lorenzo back in time and making him decline the proffered marriage at the outset." (p. 426)
Everard refuses this option on the ground that the balance of events is too precarious. But how could they have done it? Taken Lorenzo into their confidence, explained the situation and got his cooperation? Taken him back in time? Stunned the younger Lorenzo? Substituted the older Lorenzo who would then decline, instead of accepting, the proposed marriage? Hypnotized the younger Lorenzo with a false memory of having declined it? Returned the older Lorenzo to the moment from which they had taken him back in time?
But then he would coexist with the Lorenzo who had been stunned and hypnotized. Surely any scheme for taking someone into the recent past so that he can change his younger self's actions involves duplicating him? When Carl Farness offends a doorman, he thinks that:
"To jump back through time and change the incident would have violated the Prime Directive of the Patrol."
- Time Patrol (New York, 2006), p. 344.
- but it would also have duplicated you, Carl.
Incidentally, when posting about "Moving House," I meant to add that Poul Anderson's description of 1935 New York is worthy of Jack Finney:
"Here also it was fall, the kind of brisk and brilliant day that New York often enjoyed until it became uninhabitable..." (p. 342)