A couple of weeks ago, I talked about primary sources, what makes them primary and why that primary/secondary distinction might be complicated (but important!). I said then that whether a source is primary or secondary is not absolute (it depends on your questions). Nor does it determine whether a source is reliable. What, then, is a reliable source?
This is on my mind a lot at the moment because it is that time of year when the marking of student papers comes around. If you’re looking for hilarious things students write, this isn’t that place. My students are great and, if they do sometimes say things under pressure that sound a bit silly, that is all part of the learning process.
Nevertheless, without breaking that circle of trust, there are definitely things that come round time and time again. I don’t see these as student misunderstandings. They are more like the tips of ice bergs, revealing bigger ideas in society about what history is, does and is for. One of those glassy peaks is reliability.
History ought to be reliable. That isn’t a misunderstanding. It is pretty crucial. If history isn’t reliable, it isn’t much good, and may even be actively bad. What we mean by reliable, though, is trickier and has also given rise to the myth of a mysterious beast: the Reliable Source.
The Reliable Source is less like a unicorn and more like a yeti: there is some broad agreement about its features, a general sense that it is most often found in particular environments, and some blurry, out-of-focus snapshots of something that might be one. The Reliable Source is also not necessarily a beautiful thing.

Tracking its shaggy footsteps through recent, and more distant, student essays the Reliable Source is mainly to be found, we are told, in official places - government or institutional records - or in private places, such as diaries or letters. This is because governments and institutions, unless they are known to be radically corrupt, tend to keep good records, and because in the case of private documents, what is the point of lying to yourself?
The shape of the Reliable Source can be traced mainly from the things it does not exhibit: it should not include any obvious myths, legends, magic or religious feeling. It should not sound too personally emotional and it should have lots of detail.
Most importantly, a Reliable Source should be clearly distinguishable, by comparison with a range of other Unreliable Sources. These are sources which can safely be discounted (except when they support a chosen point) because they were made to present a particular point of view on an issue (bias!), were produced by a person or people with a specific agenda (propaganda!), because they are too short, too vague, too confusing or have too much woo-woo in them (defined as monsters, magic, miracles and other direct divine intervention in the course of events).
The problem with this facsimile of a Reliable Source is that it overlaps quite closely with what we might reasonably mean by reliable history, but at the same time is nonsense. Like the yeti, it occupies the uncanny valley between fantasy and possibility.
Government and institutional records may indeed need to be correct about certain things, but there are myriad ways in which that might make them unreliable for particular kinds of historical inquiry. We may not understand what was useful to be recorded in comparison with what actually happened. It may have been vital for government officers, for example, to show targets being met, even if they were not. And where do we even start with the idea that people don’t lie to themselves (ourselves)?
What do we do about sources for periods, or issues or groups, in which material simply does not exist without holding a position, caring about the matter or inhabiting a belief system that is not shared by the conventions of the historical profession? (For what it is worth, it has been well-established int he Western tradition since the fifth century BCE that writing about human choices, chance events and the interaction between them is a valid way to understand the past, regardless of the scholar’s personal beliefs. Aside from some quite specialist sub-fields and journals, the assumption is that our explanatory frameworks come without a deus ex machina option for when the going gets tough, regardless of whether the whole machina is perceived as having a deus outwith or not.)
One way of dealing with sources from such times or contexts is to try to read sources minus the woo-woo. We can believe this (hypothetical) medieval writer when he says that bad coinage caused an economic crisis (because that is a ‘rational’ thing that we know could happen) but not when we says that God caused his untimely death as a punishment for his sins.
But, what if the person writing attributed the issuing of bad coinage to that emperor because they thought that was the sort of thing a morally bad emperor would do? It may be true that bad coinage might cause an economic crisis, but the fact that it can happen might not mean that it did in this case. Both the ‘rational’ and the ‘irrational’ accounts of this emperor’s reign might have been equally shaped by the author’s religious perspective.
(This is not, by the way, an example made up on the spot. Michael VII of the East Roman/Byzantine Empire was for a long time blamed, because primary sources from the time said so, for debasing the gold coinage of the empire and thereby causing economic difficulty. That was until metallurgical studies in the 1970s and 1980s revealed that the gold content of the coinage had been dropping for nearly a century before his reign. It just turned out that it becoming visibly bad enough to be obvious, and Michael having a bad rep among near-contemporary writers made him an easy mark. He did not, however, die an early death. He was deposed, became a monk and arguably had a more successful career in the church than he had as emperor.)

Much historical research is about understanding just how many turtles deep the impact of personal and collective world views on our understanding of the things we see and experience goes. (Current consensus: pretty deep and counting.)
Another way of deciding whether a source is Reliable (capital R) is to see if some of the points it makes are corroborated by other sources. If a lot of them are, then it might be safe to assume that things in it which are not found in other material are also trustworthy, right? Again, this isn’t a completely stupid assumption to make, but it isn’t difficult to find ways in which it goes wrong, or could be wrong without us knowing.
What if the corroborating sources are actually linked to it? They might share a common origin source or just the same ways of making sense of the world? There is a great genre of historical article shaped like this: hey, everybody in [specific field of study]! Have you all realised that sources A, B and C, which everybody treats as three separate accounts of the same thing were all copying the same original source D, and so don’t actually corroborate each other at all?
And, of course, reliable is not the same as useful. A cast-iron, rock-solid, metaphorically unimpeachable source about volumes of water usage Roman public baths (which I have made up: as far as I know such a source does not exist) isn’t much use if what you want to know about is attitudes towards child marriage among the social elite (which totally did exist in the Roman Empire).
Ultimately there isn’t a convincing way to locate a yeti because, subject to quite a startling new discovery, they don’t exist. That does not, however, mean that looking for them can’t turn up all sorts of interesting new things. Likewise, the Reliable Source is a wild goose chase (a phrase which has always confused me, since wild geese indisputably do exist…), but that doesn’t make the different ways we might look at a source’s reliability useless.
All of the methods I have outlined here for identifying a Reliable Source generate incredibly useful questions to ask and try to answer. They won’t provide a certificate of fitness, but they will open up a tonne of useful questions, and sometimes new discoveries. And put enough sources about a particular thing through these questions, then stick them together in different ways until one stands up stronger than the rest and you probably have a Reliable History.