How far is it possible to know the truth about what really happened in the past?

I was up all morning doing my Theory Of Knowledge essay. I put it online just to give my readers a bit of insight into my interpretation of what history is. Feel free to contradict me and comment on your own views. In essence, isn't this what Theory Of Knowledge is all about? 

TOK essay: How far is it possible to know the truth about what really happened in the past?

The word “past” is defined as “something that has existed or occurred in a time previous to the present”. In retrospect, it is impossible to define past with a time frame of reference. In the case of this definition, it is the “present” that we use as a time frame of reference. Therefore the past is relative. The “past” for me six years into the future is difference than the “past” for me in the present.

In that six months that have passed, it would be almost impossible to know everything that happened. Assuming that what I have done in that space has no significance to any other parties, the only thing that I can truly rely on is my own memory (primary sources) or the written work that I have done in that period of time (secondary sources). For example, it would include a journal that I have written, or any sort of work that I have done to determine what I would have been studying at that point in time. Because my work has no significance to other parties, there will be no eye witnesses besides mine, which would most likely be bias so as to put myself in a better light.

On the other hand, it is quite impossible to say that my assumption is true. In a densely populated area like a city, it is impossible that your actions have no significant meaning to the other person. For example, in the case of the work I have done, my work gives relative significance to the teacher that marked it. Therefore he or she can give testimony on the surrounding period of time of which the work was handed in, albeit in her probably biased perspective.

In all cases in my examples, history is biased according to the testimony of the eye-witnesses, with the truth being a written text unrelated to any testimonials. Therefore it is true this unrelated written texts that we find the lack of bias in possible inferences on the past.

What about the past that is centuries or even millennia ago such as the bible to investigate the time of Jesus in the New Testaments roughly two millennia ago or the time of Moses and Abraham three or four millennia ago? Can we assume that the same extent of bias applies? Of course, as the saying goes “we are only human” and an atheist would say “yes, there is bias”. However according to religious people, such as my mother, would say that ‘they are written under the influence of the holy spirit to pass on to younger generations, the holy spirit being perfect, there is no bias whatsoever’.  The fact that it is written in the form of a third person narrative for (old testament books) makes it look more so despite the fact that the author and the main character is the same person.

Therefore it is belief as well which has a play of what we believe is to be true. The inference on the creation of the world for example, would be different for a creationalist than an evolutionalist. This is why in Theory of Knowledge we often think of history as ‘what we believe to be true’ and that belief is different depending on the person. In conclusion, the past can only be true to the extent that we believe it, for it is impossible to remove the bias and beliefs that you had before and thus make a bias interpretation, even more so when religion is involved.