This chapter reviews two more aspects of the policy process. The first is what policy scholars call policy design, which is the process by which policies are designed, through both technical analysis and the political process, to achieve a particular goal. Deborah Stone argues that efficiency is more a means to an end, rather than a goal in itself, but she treats efficiency as a goal because many policy advocates promote efficiency as something worthwhile on its own merits. Two other goals that seem to conflict are security and liberty. A causal theory is a theory about what causes the problem and what intervention would alleviate that problem. Closely related to the causal theory is the choice of policy tools, or policy instruments, which can be used to create a desired outcome. Economic models of policy tools focus on individual freedom, initiative, and choice, therefore tending to value non-coercive tools over those that are more coercive.