In the preceding chapters we laid down our theoretical framework and gave a systematic overview of the central problems of a philosophy of development. Our interest is in the manifold ways in which people conceptualize their world and in the foundations of such conceptualizations, especially as they develop through time. For most people, the concept of development is associated almost exclusively with the child's journey from birth to adolescence, or with a series of stages starting with an individual's prenatal life and ending with old age. However, there is no reason to conceptualize development exclusively along the age axis, or only with respect to individuals. In some domains the endpoint of a developmental sequence is normally reached with adulthood; while in other domains developmental sequences begin only with old age. Moreover, we can identify forms of conceptual development in collective processes as well.