“The lack of definitive answers to questions discussed in this book also
reflects the fact that science is an ongoing process in wh ich the most important sign of progress is often that results of an experiment or observational study lead to a new set of questions. This is part of what makes science exciting and rewarding for scient ists, but it entails an important dilemma: how do we make the best pract ical and even ethical decisions based on incomplete scient ific knowledge?”