How did Heidegger describe human beings as being-in-the-world?

In his seminal work Being and Time (1927), Martin Heidegger rejected the traditional Cartesian view of the human individual as a "thinking subject" or "mind" isolated from the material world. Instead, he introduced the concept of Dasein (literally "being-there") to describe human existence as fundamentally "being-in-the-world".1234

Heidegger argued that human beings are not entities sealed off within themselves; rather, they are inherently caught up in, involved with, and committed to other individuals and things. Key aspects of this description include:23

• Unitary Existence: Dasein is a concept of the human individual as a whole, rather than a compound of mind and body, avoiding the sequestration of human functions into a "mental" compartment.14
• Disclosive Nature: By being "in the world," Dasein acts as the locus where entities "show themselves" and are uncovered as what they are.14
• Practical Engagement: Our primary relationship with the world is one of practical involvement and commitment, which is ontologically more basic than self-conscious reasoning or abstract thought.23
• Temporality: Dasein is "out ahead of itself," characterized by an anticipatory temporality that orients it toward its own future possibilities.145