When I was thinking about how to develop an Artificial Intelligence program, I realized that boolean logic is good for computer circuits, but the real world needs a "3 state logic" that has a "time component" I will call "maybe".

So to think like a human, your logic descisions would be one of "yes no maybe". The "maybe" traverses time, because it means "will be determined later". Now the problem becomes how to keep track of all the "maybe's" and go back and redo all the previous logic once a certain unknown becomes known.

It seems that your "but" operator, is similar to my "maybe", it's a descision defered to a later time.

P.S. At first I thought this was a joke, you telling your girlfriend you want some but. :-)