Simmel regards the stranger as a unique sociological category, physically close to the community in which s/he lives, but culturally remote from it. The stranger is neither an insider, who is part of the community, nor an outsider, who has no relation to it. Simmel's primary example of a stranger is a trader or merchant, who has to deal with and fulfill an economic role in communities of which s/he is not a part.

Undocumented immigrants fit into the "stranger" category in much the same way as traders, though generally at a lower socio-economic level. These immigrants fulfill vital roles in many communities, providing agricultural and horticultural labor, along with many other services such as home maintenance and childcare. These latter roles, in particular, bring them into very close contact with insiders in the community, spending many hours inside their houses and becoming more familiar with certain aspects of their lives than friends and family.

However, at the same time, these immigrant workers are often cut off from the communities in which they live by various alienating factors. These may be as fundamental as unfamiliarity with the language, but there are also likely to be cultural and economic differences which prevent them from mixing socially and entering the community. This often obscures the importance of the contribution that undocumented immigrants make to the community and the economy and leads to political debates mentioning them primarily as a problem, rather than as contributors to society.