Because you don’t necessarily know which agent you are. If you could always point to yourself in the world uniquely, then sure, you wouldn’t need 1P-Logic. But in real life, all the information you learn about the world comes through your sensors. This is inherently ambiguous, since there’s no law that guarantees your sensor values are unique.
If you use X as a placeholder, the statement sensor_observes(X, red) can’t be judged as True or False unless you bind X to a quantifier. And this could not mean the thing you want it to mean (all robots would agree on the judgement, thus rendering it useless for distinguishing itself amongst them).
It almost works though, you just have to interpret “True” and “False” a bit differently!
Because you don’t necessarily know which agent you are. If you could always point to yourself in the world uniquely, then sure, you wouldn’t need 1P-Logic. But in real life, all the information you learn about the world comes through your sensors. This is inherently ambiguous, since there’s no law that guarantees your sensor values are unique.
If you use X as a placeholder, the statement
sensor_observes(X, red)can’t be judged as True or False unless you bind X to a quantifier. And this could not mean the thing you want it to mean (all robots would agree on the judgement, thus rendering it useless for distinguishing itself amongst them).It almost works though, you just have to interpret “True” and “False” a bit differently!