The history of second-wave feminism provides a vivid illustration of the tensions between cultural essentialism and universalism and of the dangers associated with each pole. Perhaps from that history we can glean lessons of use to the project of this book. This chapter suggests the following: Scientific cultures manifestly vary over time and space. If their aim is to provide reliable knowledge about the material world in which one lives, then, to the extent to which those worlds are stable, continuous, and connected, judgment about the effectiveness, adequacy, or utility of different answers cannot be ignored. It is inevitable that scientific cultures vary, yet we must not forget that the worlds they seek to describe belong to a single planet.