S. ANTIPHOLUS If every one knows us, and we know none, 'Tis time, I think, to trudge, pack and be gone. (3.2.151)
S. Antipholus is surrounded by people that seem to know him, yet this situation is far from solving his problem of isolation. He actually feels more estranged from himself. Considering he doesn’t know any of these people, he feels like he doesn’t know the person they know (who should be him).