How can we understand the concepts of health and disease? This was the key question in Tristam Engelhardt Jr’s “The concepts of health and disease” published 50 years ago. While many scholarly discussions have taken place in the 50 years since the publication, and progress has been made, the key issues are still up for grabs. In this chapter, I will address six key questions: (i) what are the things called health and disease? (ii) To what extent and how are the concepts of health and disease value-laden? (iii) What kind of concepts are health and disease? (iv) What is the role of models of health and disease? (v) What is the relationship between health and disease? (vi) and what is the relationship between disease and diagnosis?