Most people regard freedom as being able to do what you want, but this is not the view held today by sophisticated thinkers. Policy-makers have equated freedom with non-interference. As long as no person stops you, you are free, whether you are able to do anything or not. Social activists are wary of freedom because it might interfere with their notions of social justice. Religionists are afraid of freedom because the free person might do something they hold to be wrong. And even non-doctrinaire people acknowledge that freedom must be limited in various ways, without stopping to think that unless those ways are spelled out, anyone wanting to reduce freedom can always cite some limit or other as an excuse. And these are only a few of the ways in which freedom has been reduced. The present book spells out a definition of freedom that is as strong as the common-sense notion, details a theory of the limits of liberty that does not diminish freedom, and provides a view of social justice that is not incompatible with freedom. Further, unlike most writing on this subject, the present book specifies a justification of this definition of freedom, one that is both original and robust.