 To provide a sense of the complexities that an answer to the Focal Question must address, consider two examples that take us from the ground level of common sense with which this review began to the intimate interplay between empirical data gathered by biologists and the conceptual clarification provided by philosophers that is a hallmark of thinking about biological individuals. The first of these examples was introduced into discussions of biological individuals by the philosopher of biology Jack Wilson (1999: 23–25), the second by the physiologist Scott Turner (2000: ch.2).