Hey all, still out of town but I think @mikerod's answer here and @wparker's answer in the forum are on target. I kind of regret adding retract! at all since it's such an easy way to shoot oneself in the foot. (This isn't the first time it has caused confusion.) I'm tempted to deprecate it, or move it into a specialized package to make it clear. I don't think there is a great way to "fix" retract! when interacting with truth maintenance, since it's semantics conflict with what the engine does. Looking back on it, it feels like it's the equivalent of a GOTO statement for expert systems.

:thumbsup:

so it is "retract! considered harmful"

maybe just a part of Clara docs that gives that big warning