Summary of Adam Morton Should we Colonize Other Planets? (Polity, 2018) We are near to being able to attempt to colonize other planets in the solar system, especially Mars. Is it a good idea? Weighing the costs and benefits is more of a philosopher's task than one might at first think, for two reasons. There are issues of incomparability, involving interests of a few largely well-off people and nations in comparison to the basic needs of many, and the interests of humanity in comparison to those of the planets and other living species. And there are issues of what we should and care about in the future of our species and its descendents, rather analogous to issues of personal identity. Does the best attitude prioritize people as they are now, with the desires and values that they have. Or is it better to prioritize intelligent beings that will exist and the perhaps superior aims that they will have? The discussion needs both a scientific background and comfort with tricky issues of value. In this book I begin with an exposition of present plans for Mars colonization and the obstacles they face. I also estimate direct monetary costs and indirect opportunity costs. I then list some of the dangers of these plans and try to evaluate their chances of providing a refuge that would evade possible fates of humanity on earth. Then, in the last chapter, I get to issues about what we should prefer for the long-term future of intelligent and other life. My discussion of these relies on a distinction between wants and values, and a deliberate suspension of the assumption that there is anything ultimate about present-day human beings. In a definitely contestable final section I argue that colonization plans as presently conceived are unlikely to achieve their ends and have a high chance of unwanted side effects. Table of contents 1 Escape from Earth? 1 2 The Colony Solution 22 3 Problems with Colonies 40 4 Costs of Colonization 57 5 Colonization without Humans 78 Conclusion: Why Human Colonization is a Bad Idea