Philosophy can be done by itself (primary) or to support other activities (secondary). It can help you do better problem solving and learning regarding any topic. So you can pursue philosophy as a means to other ends, or as an end in itself. (There are many types of philosophy; I'm mostly talking about philosophy related to rationality, critical thinking and knowledge.)
This is a companion discussion topic for the original entry at https://criticalfallibilism.com/philosophy-as-a-secondary-skill/