This type of health communication enables the public to understand a health issue more thoroughly, providing them with the tools necessary to challenge or change existing power structures within their own communities. Advocacy is often associated with risk communication, the process of explaining natural disasters, human-made hazards, and behavioral practices to the public in a way they can understand. Theorists such as Don Nutbeam propose a need for advocacy and say that health literacy, or people's ability to access and make decisions with health information, is an important part of empowerment.[45] Nick Pidgeon and Baruch Fischhoff say that communicating complex medical or health information to the public is difficult because past scientists failed to base their communication on solid principles and evidence.[46] Based on these past failures, Pidgeon and Fischhoff argue for a simpler and trustworthier model of science communication.