At some point in our human history, we decided that we'd be better off working in groups. That realization spawned a whole lot of philosophizing, theorizing, and debate on how, why, and for what purpose humans function in groups. Today's Deep Dive will explore some of the foundation of what is known as "Social Contract Theory."  Do humans work together because they value equality? Or because they're afraid of their neighbor? Are the best leaders ones who rule through fear or through the promise of mutual benefit? Each of the contract theories we review today will offer some insight in to these questions and continue to improve our understanding of ourselves and the world.