How did Martin Heidegger describe Being-with-others?

In his seminal work Being and Time, Martin Heidegger rejected the traditional philosophical view of the human individual as a cognitively isolated "thinking subject." Instead, he argued that the fundamental character of Dasein—his term for human existence—is "Being-in-the-world," a state of already being caught up in, involved with, or committed to other individuals and things.12

Within this framework, "Being-with-others" is an ontological concept used to describe how Dasein is inherently connected to others as part of its basic structure of existence. By defining Dasein as "being-there," Heidegger emphasized that human existence is not sealed off within a private mental compartment; rather, individuals are fundamentally engaged with the world and those around them. This perspective serves to dismantle the Cartesian abstraction of the individual as a subject distinct from the world, positioning practical involvement and social commitment as more basic to human existence than isolated thought.123