"By 'others' we do not mean everyone else but me--those over against whom the "I" stands out. They are rather those from whom, for the most part, one does not distinguish oneself--those among whom one is too. This being-there-too with them does not have the ontological character of a being-occurrent-along-'with' them... This 'with' is something of the character of Dasein; the 'too' means a sameness of being as circumspectively concernful being-in-the-world. 'With' and 'too' are to be understood existentially, not categorially. By reason of this with-like being-in-the-world, the world is always the one that I share with others. The world of Dasein is a with-world. Being-in is being-with others."

from Heidegger's "Being and Time"