Book excerpt: Autonomous cars, drones, and electronic surveillance systems are examples of technologies that raise serious ethical issues. In this analytic investigation, Martin Peterson articulates and defends five moral principles for addressing ethical issues related to new and existing technologies: the cost-benefit principle, the precautionary principle, the sustainability principle, the autonomy principle, and the fairness principle. It is primarily the method developed by Peterson for articulating and analyzing the five principles that is novel. He argues that geometric concepts such as points, lines, and planes can be put to work for clarifying the structure and scope of these and other moral principles. This geometric account is based on the Aristotelian dictum that like cases should be treated alike, meaning that the degree of similarity between different cases can be represented as a distance in moral space. The more similar a pair of cases are from a moral point of view, the closer is their location in moral space. A case that lies closer in moral space to a paradigm case for some principle p than to any paradigm for any other principle should be analyzed by applying principle p. The book also presents empirical results from a series of experimental studies in which experts (philosophers) and laypeople (engineering students) have been asked to apply the geometric method to fifteen real-world cases. The empirical findings indicate that experts and laypeople do in fact apply geometrically construed moral principles in roughly, but not exactly, the manner advocates of the geometric method believe they ought to be applied.