Lots of very interesting interpretations! My take is that the story teller and Alison were a couple until she cheated on him at a party with his friend. He dumped her and she shows up pregnant and suggests the baby is his and wants to get back together with him. He says the kid isn't his and doesn't want to have anything to do with her because he knows(aim is true) that she's not right for him.
There is another later encounter and now she is unhappily married and once more she suggests they get back together but he knows that it would never work and wishes she would stop the silly talk and forget the idea of them(big light like the lightbulb metaphor for an idea). He is honest and knows himself and Alison very well(aim is true) and that she can't be trusted.
Lots of very interesting interpretations! My take is that the story teller and Alison were a couple until she cheated on him at a party with his friend. He dumped her and she shows up pregnant and suggests the baby is his and wants to get back together with him. He says the kid isn't his and doesn't want to have anything to do with her because he knows(aim is true) that she's not right for him. There is another later encounter and now she is unhappily married and once more she suggests they get back together but he knows that it would never work and wishes she would stop the silly talk and forget the idea of them(big light like the lightbulb metaphor for an idea). He is honest and knows himself and Alison very well(aim is true) and that she can't be trusted.