Philosophy is defined in multiple ways throughout the document. It is described as the love of wisdom by its Greek and Latin origins. Several philosophers provide their perspectives, such as Socrates viewing it as examining how we should live, and Marx seeing it as interpreting the world to change it. Key branches discussed include logic, ontology, epistemology and ethics. Logic is defined as necessary reasoning by Aristotle. Ontology deals with the nature of existence and phenomena. Epistemology concerns the nature and scope of knowledge. Ethics is deduced from the Greek word for custom regarding behavior. The document argues for putting philosophy back into PhDs by training students to think critically and view their work through a lens of social responsibility.