Improving living conditions of the poor often involves a drastic change in lifestyle, in order to fit daily life into industrially produced dwellings. Slum rehabilitation programs replacing informal settlements with standardized mass housing, have often resulted in a mismatch of inhabitants and their built environment. Participation strategies meant to counter this problem, show little effect unless the user is in charge. What is the problem with development and participation? This chapter will discuss ‘housing the poor’ as a case to illustrate how industrialization and systemization are at odds with participation. We will consider two ways of producing housing: industrial mass housing, and informal settlement. The focus is on the connectedness of the user, the inhabitant, with his dwelling. It will lead to the observation that participation aims at meeting the diversity that is natural to human beings, whereas systemization requires and produces the opposite: uniformity. Moreover, the term user-participation implicitly states the user is an outsider participating in developers' projects, which after all are dominated by the interests of the construction industry. An Appropriate Technology - approach in housing the poor would benefit from a focus on user-building interaction as it taps directly into people’s most powerful resource: creativity. Western systemization is not the only route to improvement. Strategies based on vernacular are at least as effective, appropriate, and humanly sustainable.