A patient holds a fixed, false belief. Before revealing the answer, decide what single question distinguishes a primary delusion from a secondary one.

Ask whether the belief can be traced back to, and understood as arising from, some other underlying morbid experience — depressed or elevated mood, a hallucination, personality, or stressful life events. A secondary delusion can be understood in light of such a starting point; a primary delusion cannot be traced back in this way at all, appearing as something genuinely new rather than an elaboration of a prior experience. This is a question about the belief's origin and comprehensibility, not about its content, its degree of conviction, or how bizarre it sounds — a delusion can be primary or secondary regardless of how ordinary or strange its content is.