UPSC and IAS Mains - Is Philosophy a good optional subject. Philosophy is an optional subject that is reasonably popular among IAS aspirants. It may not be as popular as history or public administration, but it still fares better than many other subjects.The syllabus is short though it will take some time to understand it in the beginning. But once you have understood it completely it will take comparatively less time to revise it. Philosophy is a classic subject.