This chapter by Ian Mitroff in a forthcoming edited book describes how the history of Western Philosophy offers five primary modes of obtaining valid knowledge, or how one defines and discovers "Truth." This chapter is valuable pre-reading for the MSR Research Collaborative's February 23, 2021 webinar where Ian Mitroff describes these five modes of obtaining valid knowledge and discusses the implications of each for research questions, research methods, publishing, tenure, and impact on the world.