Social scientists have long sought to understand how and why individuals live together—especially in dense settings such as those found in urban environments. In The Division of Labor in Society, Emile Durkheim outlined two theories that attempt to explain how social order and solidarity is established and maintained. Solidarity describes connections between individuals that allow them to form a cohesive social network. Durkheim argued solidarity is significant because it is a necessary component of a functioning civilization and a necessary component of a fulfilling human life.
Durkheim described two forms of solidarity: mechanical and organic, roughly corresponding to smaller and larger societies.
Mechanical solidarity refers to connection, cohesion, and integration born from homogeneity, or similar work, education, religiosity, and lifestyle. Normally operating in small-scale "traditional" societies, mechanical solidarity often describes familial networks; it is often seen as a function of individuals being submerged in a collective consciousness. Collective consciousness is achieved when individuals begin to think and act in relatively similar ways. Though traditional small towns, familial networks, and religious congregations are often cited examples of mechanical solidarity, dispersed religious communities would also qualify if they can be said to share a collective conscience.
Organic solidarity is born from the interdependence of individuals in more advanced societies, particularly professional dependence. Although individuals perform very different roles in an organization, and they often have different values and interests, there is a cohesion that arises from the compartmentalization and specialization woven into "modern" life. For example, farmers produce the food to feed the factory workers who produce the tractors that allow the farmer to produce the food.