Heidegger's Being and Time has been criticized as solipsistic in its focus on individualized Dasein, whose conscience has called it out of the world of the "they," into an authentic Being-unto death. The argument in this thesis is that Heidegger's fundamental insight can be defended against this criticism, but that it needs to be supplemented, to avoid misunderstanding, with concrete detail concerning important features of our relations with others. Marcel has provided the necessary corrective by underscoring the vital element played by the other in our own development. The thesis explores central Heideggerian ideas, such as Dasein's advance toward death and resoluteness in the face of fateful existence, with a view towards providing space for a more satisfactory account of concrete relations with others.