Post-modernity is not really a separate thought-world from modernity - it is its extension I think. One of the fashionable "ideas" associated with post-modern thought is that all subjects are biased with regard to their observations. Now this is an idea that modernists certainly knew about, and it is one of the reasons that critical thinking and the scientific method came into being - to create a space for reasoned thinking that was not under the influence of theology. Post-modernism has taken this in a self-reflective sense, suggesting to us that this critical alternative is, in itself, not without its biases. This has led to a relativism and the observation that "truth" is a function of power and a function of the perspective of the observer. It is not an accurate description of an external "objective" reality.
I don't think I'm alone in my opinion that when this degrades to complete relativisim, the philosophy falls apart, becoming exceedingly superficial. It leaves us floating in a sea of nonsense, vagueness, even nihilism, especially in terms of ethics, but also in terms of "doing history." Just because all observers are biased, does not mean that all reconstructions of history are of equal worth historically, as some are trying to conclude. I think that this perspective is an unfortunate application of the post-modern observation to serve the needs and desires of some in the theological community who have felt their "histories" marginalized by modernists.
The historian's position is not without biases. But what should those biases be? To be as impartial as possible (and recognize when we aren't), to provide a reconstruction of history whose goal is to be as self-consistent with the general experience of humanity as possible, to be guided by critical thought processes and reason, and to be as fair and consistent with the sources as she can. It is these biases that I own as my own. It is from these that I operate. And it is my hope that more biblical scholars will self-reflect, and push themselves to become uncompromising in their historicism.