A person may attach a condition to his eruv and say, ‘If gentiles come from the east, my eruv is to the west; if from the west, my eruv is to the east; if they come from both directions, I shall go to the place I choose; if they do not come from either direction, I am as my townspeople.’ ‘If a scholar comes from the east, my eruv is to the east; from the west, my eruv is to the west; if ones comes to here and [one comes] to there, I shall go to the place I choose; if to neither direction, I am as my townspeople.’ R’ Yehuda says: If one of his scholars was his teacher, he must go to his teacher. But if both were his teachers, he may go to the place he chooses.