How legitimate can history be if every document that has ever been written has some bias behind its writing? To what extent can we trust historical books written in a time we otherwise would have no knowledge of? How certain can we be that the "history" we're taught actually happened? And finally how do historians classify something as historical, what qualifications does a document require to become historical? Thanks for the help, Alex.

Why do you think inquiry into what happened in the past is anydifferent from inquiry about what's happening on the other side of theMoon? In both cases, we lack direct access to the facts. We must makeinferences, based on many assumptions, from what we do observe to whatactually was (or is) the case. Do you think history is differentbecause there's something different about the past? (We could inprinciple visit the other side of the Moon, but we simply cannot --barring time travel -- visit the past.) Or do you think history isdifferent because it focuses on the actions of people, and some kind ofdistortion always infects our reasoning about people that does not leadus astray in our inquiries into the natural world?

Presuming that it is impossible to write unbiased history, does that make the discipline invalid in that it can never be what it would ideally (at least for many) be: a completely truthful presentation of the past?

I'm not sure what you're presuming until you say what "biased" means. Do you believe that contemporary physics is biased? If not, then what is it about historical research that makes it impossible for historians to attain the same degree of rigor and truth that physicists do? And if so, then what would inquiry have to look like in order for it to be "unbiased"?

Why do historians write as if Man were the pre-eminent factor in shaping events when so much is decided by scientific factors (and negative ones, like the absence of viruses and meteors)?

It seems to me that what we call "history" is largely concerned withthe description or explanation of past episodes in the social, political, military,artistic, intellectual, etc. life of humans. Study of past episodes of non-human activity, for instance, the movementof tectonic plates and the formation of stars, tends to go by other names, like "geology" or "astronomy". So perhaps it's no wonder that the doings of humans take center stage in what we call "history". (That said, plenty of histories do deal with the human consequences of natural events beyond our control.)