(en) This thesis advances the philosophical debate on how work should be morally evaluated and regulated through four articles. The first introduces the concept of fruitful work, understood as work that makes a net positive contribution, and argues that fruitfulness is the internal good of work. The second examines the badness of the reserve army situation, in which employers hold power over employees through the credible threat of replacement by unemployed workers. It argues that solidarity is necessary to explain what is bad about this situation. The third and fourth articles apply a “justice as fair cooperation” approach to involuntary unemployment and to job inequality, showing that neither involuntary unemployment nor job inequality can be resolved through income redistribution. Taken together, the four articles lay the foundations for a “justice as fair cooperation” approach to work.