I am mulling over methodologies and approaches for answering research questions like, for example, "Was pickling used to preserve food in England between 300CE and 1200CE?". It is entirely possible, of course, that the answer to this is "there is no evidence either way", but let's ignore that for the purposes of discussion.

We can look at contemporary texts (annals, accounts, hagiographies, letters, recipes, etc, where these exist) for mentions of pickling. This runs into some language difficulties - it is very difficult for a translator who doesn't have moderately specialised language to distinguish between words that mean "salted", "cured", "pickled", "brined", "fermented" or just plain "preserved", should those words exist at all, or have those concepts in that exact division. And without the aid of a good translator, it is difficult for the non-language-specialised historian (in this case, the food historian) to know what the obscure words are at all. We can also, in theory, look at the etymology of the words used to describe food preservation. If a word for 'pickle' exists, we could reasonably assume that something was indeed pickled (and then we can look for instances of that word, which leads back into the above).

We can look for images of pickling or other preservation in illuminations, scuplture, and other depiction. This assumes, broadly, that we can tell one activity with a barrel or vat from another, if indeed there are such depictions.

We can look for direct evidence; the remnants of pickle barrels in archaeological discovery. This assumes, as with depiction, that we can distinguish a pickling vessel from any other, and that's not particularly clear. Any vessel on which vinegar could leave distinguishing marks is almost by definition not suitable for use with vinegar, too. It might be possible for really good archaeobotanic work to distinguish 'seeds which were pickled' from 'seeds which were not pickled', although I suspect that's wishful thinking on my part. It is just about possible that certain circumstances might give actual containers of pickled goods still extant, though I am not holding out much hope.

We can look at circumstantial evidence - the import of large amounts of salt and/or vinegar, for example. That might be seen in accounts, inventories, or archaeological evidence. If we were very lucky, we might find intact barrels or other containers of salt, or amphorae still containing vinegar. Because the salt in particular had to be imported in quantity from places that had salt supplies, this is not quite as hopeless as it might seem. Also in this category is the effect of vinegar on people's teeth - a diet high in vinegar leads to softer enamel, which can be identified in remains by someone who knows at what they are looking. This is under the heading of circumstantial because there are plenty of other things that also soften enamel.

And finally, we can look at the places and frequencies in which pickling is found outside our stated period. If we find evidence of widespread pickling from Southern Scotland down to Cornwall in the later 1200s (which, sadly, we do not), then it is more or less fair to assume that that did not spring into being in 1201, but was there, undocumented and unevidenced, for some time beforehand.

Are there other approaches I'm missing?

I would really like to know a good book on the philosophy of history, or a place where I could learn more to contribute about the philosophy of history.

What is the current historical consensus (or nearest thing to a consensus) on the old intentionalist versus structuralist (versus synthesis?) debates in Third Reich historiography?