The theories of collective action relating to natural resource managementand agricultural development are often considered to be polarized. The theories are divided into institutional economics with a focus on social dilemmas and sociology/anthropology. This article reviews the attempts to find common ground between the two groups. Several studies in sociology and anthropology have pointed out weaknesses in the approaches based on institutional economics. However, the criticisms have failed to trigger serious debate. Studies in each group have taken the initiative to “reach out” to the other, but so far the results have been limited. This article proposes an alternative approach to finding common ground between both groups. This involves focusing on the scales of validity of the research, i.e. the scale at which research results are considered valid. Many studies use or develop theoretical bases and build methodologies in order to obtain results that are deemed to be valid at a local or global scale. Other approaches use a meso-validity scale, e.g. one economic sector or one type of natural resource in a specific region. Some of these approaches organize a structured comparison between different cases of collective action and, at the same time, address the criticisms made by sociologists and anthropologists with regard to the approaches used in institutional economics. Research at a meso-validity scale can help establish common ground between the two main groups of theories concerned by collective action.