In secondary sources, authors analyze and interpret primary source materials.
Secondary sources can be scholarly or popular. Scholarly sources (sometimes called "academic" or "peer-reviewed" sources) are written by and for experts and typically include bibliographies and citations. Popular sources are written for a general, non-expert audience and can be authored by anyone.
If your topic has been approached from other disciplinary frameworks, you may wish to familiarize yourself with that scholarly literature, with the aim of showing how a philosophical approach can add to our understanding of the issues. Use the library's subject pages to explore more options.