To make an argument from silence is to express a conclusion that is based on the absence of statements in historical documents, rather than their presence. In the field of classical studies, it often refers to the assertion that an author is ignorant of a subject, based on the lack of references to it in the author's available writings. Thus, in historical analysis with an argument from silence, the absence of a reference to an event or a document is used to cast doubt on the event not mentioned. While most historical approaches rely on what an author's works contain, an argument from silence relies on what the book or document does not contain. This approach thus uses what an author "should have said" rather than what is available in the author's extant writings.

Argument from ignorance, also known as appeal to ignorance, is a fallacy in informal logic. It asserts that a proposition is true because it has not yet been proven false or a proposition is false because it has not yet been proven true. If some proposition has not yet been proved true, we are not entitled on that ground alone to conclude that it is false and vice versa. In debates, appealing to ignorance is sometimes an attempt to shift the burden of proof. The term was likely coined by philosopher John Locke in the late 17th century.