OP here.

Great question. Thankfully most of the topics I'm covering here are well covered by trusted sources that are freely available on the internet. This is particularly true about dates (e.g. when a particular philosopher died). Separately, many of the articles are less about the specific history of each topic, but about how the topics fit together and what you as a reader might like to think about as a result. These parts aren't stating facts (which can be true or untrue) but explaining that there's a different way to look at something (which is matter of opinion or perspective).