This, however, can be a tricky one due to all sorts of biases involved. An event happens and time passes until it is written down. With time the accuracy starts to degrade with some decay function. Then there is a problem if biases and points of view, the recorded event is at maximum only as accurate as the author's observation. The skill of the author to describe the events can also bring the accuracy into question. Elizabeth Loftus talks about the creation of false memories which is hardly a malicious intent but throws even more uncertainty into the mix.
Maintaining trust in the record is an incredibly difficult undertaking. My theory is that most of us just close our eyes and pretend everything is OK unless something obvious stand out. Of course as a society we put various means of alleviating the problem of trust. Means such as the use of references, language standards and peer reviews. All of which reduce to some form of trust in a person. These approaches probably work well assuming that most people are not malicious is nature.
It is a lot easier to trust the accuracy of this type of writing because the entities being described have either been documented somewhere else (shifting the validation from the writing in question) or they are ideas created by the author. Ideas created by the author can be assumed to be 100% accuracy because the writing in question is the first instance where the idea enters the world. The only other place the idea exists is the author's head which we cannot compare the accuracy to.
The intent in writing for the sake of discussion is to show a trail of thought. Probably everyone can remember C follows B follows A but what if there are 30 steps. That requires writing things down, perhaps with the author as the only audience. For example, one of the purposes of this blog is to help the author organize his thoughts of experimentation.
In almost every case a piece of writing will contain several of these forms. In some cases the art will be pervasive through the entire piece, however others can be mutually exclusive in different parts of the written piece. When the author puts their art into the writing, the readers enjoy it more.