Research-based writing depends on the writer's ability to locate relevant sources and assess their credibility, currency, and relevance before incorporating them into an argument. Sources range from primary (original documents, data, artifacts) to secondary (analyses and interpretations of primary sources) to tertiary (encyclopedias, textbooks that synthesize secondary sources), and each type serves different argumentative purposes. Evaluation frameworks like the CRAAP test (Currency, Relevance, Authority, Accuracy, Purpose) provide a systematic checklist, but skilled researchers also practice lateral reading — verifying a source by checking what other sources say about it — rather than evaluating a source solely on its own terms.
Conduct a research session on a genuine question, starting with database searches and working outward, while documenting the evaluation decisions you make about each source. Practice lateral reading: when you find a promising source, open three tabs to check the author's credentials, the publication's reputation, and whether other scholars cite the work. Compare a peer-reviewed article, a newspaper report, and a blog post on the same topic to see how source type shapes depth and reliability.
Your prerequisite on research and citation taught you the mechanics: how to format a citation, what a bibliography requires, how to integrate a quotation. This topic is about the step before all of that — deciding what is worth citing in the first place. The internet has made finding sources trivially easy and evaluating them genuinely hard. A search returns thousands of results, and distinguishing credible scholarship from polished-looking noise is now a core intellectual skill.
The source type hierarchy gives you a starting framework. Primary sources are the raw material of research: original documents, datasets, artworks, legal decisions, interview transcripts, literary texts. Secondary sources are scholarly analyses of those primary materials — journal articles, academic monographs, peer-reviewed book chapters. Tertiary sources (encyclopedias, textbooks, review articles) synthesize secondary sources into accessible overviews. Each type serves a different argumentative function: you use primary sources as evidence, secondary sources as scholarly context and conversation partners, and tertiary sources as orientation when entering a new field. Citing a textbook where you should cite a primary document is a sign you haven't done the research.
Evaluation frameworks like the CRAAP test (Currency, Relevance, Authority, Accuracy, Purpose) provide a systematic checklist, but their real value is making your implicit judgment explicit. Currency matters differently in different fields — a 1985 paper on ancient Roman agriculture is still useful; a 1985 paper on internet security is not. Authority means checking whether the author has genuine expertise in this specific claim, not just related credentials. Purpose is especially important: ask whether the source is trying to inform or to persuade, and whether its conclusion preceded its evidence.
Lateral reading is the professional researcher's key upgrade over the CRAAP test. Instead of evaluating a source by reading it carefully in isolation, you verify it by checking what others say about it. When you find a source that looks promising, open additional tabs: search the author's name to see where else they publish and whether experts in the field treat them as credible; search the publication to see whether it has a reputation for peer review or for publishing unreviewed advocacy. Lateral reading is faster and more reliable than careful internal analysis, because unreliable sources are often internally coherent while their problems are visible from outside.
The practical implication is a change in workflow. Strong researchers use databases (JSTOR, Web of Science, Google Scholar, subject-specific repositories) rather than general web searches, because databases prefilter by publication type. They follow citation trails backward (who does this author cite?) and forward (who has cited this paper since?). And they treat Wikipedia not as a source to cite but as a map: the references section of a well-developed Wikipedia article is often the fastest route to the primary and secondary sources you actually need.