Philosophy of psychology refers to issues at the theoretical foundations of modern psychology. Some of these issues are epistemological concerns about the methodology of psychological investigation. For example:

• What is the most appropriate methodology for psychology: mentalism, behaviorism, or a compromise?
• Are self-reports a reliable data-gathering method?
• What conclusions can be drawn from null hypothesis tests?
• Can first-person experiences (emotions, desires, beliefs, etc.) be measured objectively?