[kylebrown]

The other day, I ran across this in a Yudkowsky article[1]:

> Suppose that earthquakes and burglars can both set off burglar alarms. If the burglar alarm in your house goes off, it might be because of an actual burglar, but it might also be because a minor earthquake rocked your house and triggered a few sensors. Early investigators in Artificial Intelligence, who were trying to represent all high-level events using primitive tokens in a first-order logic (for reasons of historical stupidity we won't go into) were stymied by the following apparent paradox: [.. snip ..] Which represents a logical contradiction, and for a while there were attempts to develop "non-monotonic logics" so that you could retract conclusions given additional data.

1. http://lesswrong.com/lw/ev3/causal_diagrams_and_causal_model...

[dpflan]

Thanks for this, though I may not be fully comprehending. If earthquakes can set off burglar alarms, and if burglars can set off burglar alarms , why would there be no -|ALARM->EARTHQUAKE theorem? Understandably the ALARM is for detecting burglars not earthquakes, but it does function as a detector for both.

[orodley]

It doesn't function as a detector for both, it functions as a detector for either. I'm not being pedantic, there is a subtle difference. ALARM -> EARTHQUAKE is false: the correct theorem is ALARM -> (EARTHQUAKE | BURGLAR). If the alarm goes off then you have no certain knowledge about which one caused it, only probabilities.