Sometimes you come across someone making interesting claims about history, and it’s hard to tell whether you should take them seriously or not. If you’re not an expert in the field, how do you know whether to believe what you’re reading? There’s no perfect answer, and basic critical thinking will take you a long way, but here area few tips that can help set you on the right path.

Since I’m a historian of the ancient Mediterranean, my advice is particularly focused on the use of ancient texts when making claims about ancient history, but many of the fundamental principles outlined here are applicable to historical claims in any time period.

One important thing to look at is how people use primary sources, that is: documents and other texts written in the time period of the events or people in question. Here are some questions you can ask about the use of primary sources to help evaluate historical claims.

Do they engage with primary sources at all?

This is a basic one. All historical argument is based on evidence drawn from primary sources. If someone’s making claims without any primary sources to back them up, that’s reason to be suspicious.

A lack of primary sources does not necessarily mean that a historical claim is unfounded. People, especially non-historians, may cite secondary sources and modern research, but you should be able to trace the claim back through those sources and find the primary source evidence that it is based on. Some scholarship, if it is more historiographical and theoretically based, may not engage with primary sources directly, but then it will not be making claims about specific events, places, or people in history.

Do they cite their sources?

This is another basic one. In casual conversation, you don’t need to back up every assertion with footnotes and bibliography, but if someone wants their claims about history to be taken seriously, they should tell you what evidence those claims are based on. In particular, they should be able to point you to a source that you can look up for yourself to verify that it actually says what they claim it says.

Different kinds of sources have different standards for citation. With ancient texts, there are established ways of referencing specific passages. Shorter works are divided into sections or lines; longer works are divided into books, which are further subdivided into sections or lines. We never cite ancient sources by page number, since page numbers vary between different editions and translations. If someone is citing an ancient source by reference to the page numbers of a modern edition, that’s a warning sign that they may not be knowledgeable enough about the topic to interpret an ancient source with appropriate attention to its context, influences, and biases.

Do they use sources appropriate to their subject?

You should always use the right tool for the job and the right source for the claim. When someone is using a source that isn’t relevant to their argument, or isn’t using a source that is relevant, you should question whether they know what they’re talking about.

For example, our main primary source on the Peloponnesian war between Athens and Sparta is Thucydides’ History of the Peloponnesian War. Some other sources, like the comedies of Aristophanes, also provide relevant insights, but if someone is making a claim about the Peloponnesian war and doesn’t mention Thucydides, they should have a good reason why not.

Do they use non-literary sources?

The most accessible primary sources are literary sources composed with the intent of engaging readers, like the folk stories in Herodotus’ Histories or the palace gossip in Suetonius’ Lives of the Twelve Caesars. There are many other kinds of textual sources that are not literary, such as coin texts, building inscriptions, graffiti preserved in places like Pompeii, and dedicatory texts on religious offerings.

Specialized fields of study, such as epigraphy, papyrology, and numismatics, focus on finding, interpreting, and contextualizing such sources. Using such sources is often more difficult and requires more expertise and study than reading literary sources. Not every historical question has relevant non-literary sources to refer to, but if someone does reference non-literary sources in their arguments, that is a good sign that they have some real knowledge of the subject and have undertaken serious research.

Do they situate their sources in time, space, and social context?

All primary sources were produced by specific people in specific social and historical settings. We can use them most effectively as evidence for things that those people had good reason to know about. The farther the writer of a source is from the topic they wrote about, the less confidence we can have in what they tell us.

The Greek historian Herodotus and the Macedonian rhetorician Polyaenus give different accounts of how the Persian Empire conquered Egypt in 525 BCE. Herodotus traveled in Egypt less than a century after the Persian conquest and interviewed local priests about Egypt’s history. Polyaenus wrote in the second century CE, almost seven hundred years after the events, and, as far as we know, never traveled in Egypt or had any contact with Egyptians. These facts shape the weight that we should give to their different accounts, and anyone who does not acknowledge the difference is not practicing responsible scholarship.

Do they engage with the sources in their original language?

Many ancient texts are available today in good translations, and, simply for the sake of efficiency, most practicing historians will begin their research with modern translations. Serious historical scholarship must go beyond translations, however. The more that an argument relies on the meaning of particular words or on the details of what an ancient author did or did not say, the more crucial it is that we pay attention to the original words in the original language and linguistic context.

For instance, people sometimes make much of the fact that Herodotus describes the ancient Egyptians as “black-skinned.” This is a literal translation of the ancient Greek word Herodotus uses, melanchroies, but the Greek word has a different set of associations than the modern translation. To an ancient Greek, melanchroies meant ‘deeply suntanned.’ It had none of the racial implications that the English word Black has today, and historical arguments that depend on the modern translation risk misunderstanding what Herodotus was saying (and not saying).

Do they engage with sources that don’t support their argument?

Few things in history are simple. Almost any claim we can make about historical events, people, or societies is going to be contested, and there will be sources that both support and contradict it. People who want to put forth dubious claims tend to cherry-pick the sources that support (or can be made to sound like they support) those claims while ignoring the ones that don’t. How a historian deals with those contradictions is an important mark of good scholarship.

People sometimes make claims about the role of women in the Celtic-speaking societies of northwestern Europe on the basis of passing references in some ancient authors, but the writers who give us the fullest and most detailed accounts of societies in those regions—Polybius, Caesar, and Tacitus—do not describe societies in which gender relations were significantly different from those of the Mediterranean. There are sound reasons to critique those authors and question the accuracy of their ethnographic knowledge, but someone who doesn’t engage with those sources is not making a good historical case.

Do they critically examine the sources?

Just because someone wrote something down doesn’t make it true. Sometimes people don’t know what they’re talking about. Sometimes they lie. If a historian is relying on a primary source to support a particular claim, part of the argument they need to make is that the writer they’re citing actually knew what they were talking about and were telling the truth about what they knew.

The Roman historian Tacitus famously wrote that the Germanic peoples of Rome’s northern border were of pure stock, having never mixed their bloodlines with any other people. This claim has been uncritically and enthusiastically embraced by modern nationalists and racists of various stripes, but a critical reader needs to ask: how would Tacitus, a Roman aristocrat who didn’t speak any Germanic languages and probably never even visited the northern frontier, actually know anything about the long-term genetic history of the peoples he was writing about? What other ideological or literary agendas might Tacitus’ claims about the people of the empire’s northern frontier be serving–either for Tacitus himself or for whoever he relied on for his information?

As I said above, there is no perfect technique for separating good historical scholarship from bad, but these questions are a useful place to start, and applying them thoughtfully to both online discussions and claims you may come across in your research will help you find better historical arguments and avoid worse ones.

History for Writers looks at how history can be a fiction writer’s most useful tool, from worldbuilding to dialogue.