I've also struggled with the question you are posing and I've come to the conclusion that the value of history is not tied to an absolute all-encompassing understanding or knowledge of the past. Here's my answer to this question.

The hardest part about it is that you're right. We can never know all of the past, and even if we did, we couldn't possibly communicate the totality of that experience. As far as we know the only thing that can process the complexity and enormity of human experience are humans themselves. A book, no matter how well written and detailed, is only a pale shade of living experience. A book detailing every experience of a single individual is still too much for a reader to absorb or appreciate. Imagine trying to write about a family of individuals? Or something believed by a dozen individuals? A government formed by hundreds to govern thousands or millions? The effort scales far far off the radar of human capability if we were to try to recreate the past as accurately as possible.

So first we must accept the impossibility of our task comes from physical limitations as much as existential crises about knowledge. Let's say that we invent a device that does communicate the totality of experience to another individual. Some sort of mind-downloader that lets us live the uniqueness of another human's experience. We've overcome the physical barrier to communicating the whole of the past. We are still confronted by the problem of subjective experience and constructions.

Let's look at an example. You and your friend listen to Bob Dylan's "The Times They Are A-Changin" for the first time. You are immediately struck by the lines, "Come mothers and fathers / Throughout the land / And don't criticize / What you can't understand / Your sons and your daughters / Are beyond your command." Your parents had tried to control you in your late teenage years and this line makes you remember walking out of the house at 17 to live your own life. You feel happy and triumphant.

Using the mind-downloader, you live your friend's experience of the song. For your friend, every time Dylan says "for the times they are a-changin," they are racked by an even stronger emotional response. Fear, anxiety, sadness. Dylan's song isn't an expression of freedom, but a lament for an ever-changing world that will never - that can never - be the same.

Which of these two experiences is more true? Is one wrong or right given what Dylan intended the song to mean? Does it matter that one is a deeper emotion or a more shallow one? Does the commonness of your experience make it more or less valuable than the somewhat unique response of your friend?

These are not the sort of questions historians ask about the past. They are not ones that weigh the value of past events and individuals in relation to their accuracy, to their impact on others, and to what was known at the time. In short, historians examine accuracy, effect and uniqueness. Accuracy, you might say, sounds like truth, but I think there's a key distinction between asking the truth of a fact compared to the truth of the past. While examining historical sources, historians are charged with asking: Can we confirm this information? And in turn, what effect did it have? Is it a unique or common experience/source/idea?

"Is it true?" is not a question we seriously ask anymore.

Truth is relative after all. Bob Dylan's song is a thousand things to a thousand people. It can be an inspiration or a depressing reminder. You could list its sales and the money it made and it becomes a statistic which is more meaningful to some and less meaningful to others. As post-modernists suggest, despite the feeling that one might be more 'true' or 'worthwhile' than the other, both are entirely constructed. We like to imagine that the value of past experience takes a one-way street going from Point A in the past (when it occurred) to Point B in the present (when we realise its value), but it's the reverse. We impose value onto the past. We impose value on everything! That's the crux of the existential crisis that nothing has value but what we make up for it.

And that's the beauty of history. It is nothing more than the stories we tell about ourselves and only has value to storyteller and audience. From your parents telling the story of how they met for the hundredth time, to your friend's story about that one time he saw a flying pig, to the time your hometown chef won that chili cook-off in the county over, to the nation that fought the just war against fascism. As Canadian writer Thomas King says: The truth about stories is that's all we are.

In the quiet of your mind, ask yourself: who are you? Why are you the person that you are? The answer is probably a whole lot of stories about yourself whether you know it or not. You don't like broccoli because of that one time the dog threw it up. You fell in love because you had to buy flour at 2:09am. You like the summer heat because you don't like socks. You don't like socks because you like summer heat. You cry during Bob Dylan "The Times They Are A-Changing" because of all the times that changed and you weren't ready for it.

These stories are the most valuable thing about who you are. They make you who you are. Without them, you are a blank slate, an empty vessel devoid of the complex, messy, amazing individual experiences that makes us human. A person without a past is hardly a person at all.

As human gathered to form communities, they naturally did the same with their communal past experience. Just as we make up value for our own individual past experience, we began placing value on our shared experiences. The history of a villages, of kingdoms, of nations, all naturally emerges as a result of humans telling the stories of who they are. We collectively attach value onto experiences to tell the story of Canada, or of women, or the French Revolution, or of 19th century British working class families. Instead of dogs throwing up, late night flour purchases, or sockless summer days, we talk of bravery during war or grave meetings in tennis courts or the decisions of the impoverished during desperate times.

Though all experience and historical "truth" is relative to perspective, that does not diminish the worth of each of those perspectives. Sure, history is formed by constructions of society and linguistics, just look at gender, or race, or political and economic systems. They are ways for humans to try to make sense of the world. But so are the stories we tell about ourselves. I saw a dog throw up cake too, but I still eat cake and don't tell that story to anyone. I don't cry during Dylan songs, but I think about it. The story is better if I cry though. Close enough, right?

Yes lessons can be learned from these stories. We can remember things like don't eat broccoli, or don't invade Russia in winter, or always know times are a-changin'. Historians providing lessons from the past isn't really why the profession of history is worthwhile though. Like so many content-creators, we are artists. In the cacophony of infinite human experience that is the past, historians transcribe a single voice from the white noise. Or a chorus of voices or a symphony of sound. Limited as we may be by poor recordings or distorted notes, historians take the complex and make it simple. We overcome the physical impossibility of communicating the past as best we can. We are not composers but conductors, or as French historian Marc Bloch might say, not lawyers but witnesses - we do not create or indict, but we organize and observe. To use one of my favourite quotes about our profession from Johann Droysen in 1868:

History is humanity's knowledge about itself, its certainty about itself. It is not 'the light and the truth,' but a search thereof, a sermon thereupon, a consecration thereto. It is, like John the Baptist, 'not the light but sent to bear witness to that Light.

Our duty is not to speak of truth. We bear witness to the great endeavour of human existence, we worry about the accuracy, effect, and uniqueness of our stories, not the truth of them. The only truth about history is that it is all we are. The historian's task is to search and communicate the answer to that question: Who are we? Describing who we are - all of us, not just the rich white guys who wrote so many books - that is the historians' task. It is the truth and the answer for which we will always search but we will never find. Or as Droysen says, "It is not 'the light and the truth,' but a search thereof, a sermon thereupon, a consecration thereto."

Edit: I turned this into a posting on my blog, which you might enjoy if you liked this post.

I'm a big fan of postmodernism. It's all very interesting. The thing you have to watch out for, though, is that you don't fall down the rabbit hole. It's easy to get a sense of hopelessness about history because it swipes away the entire basis of what traditional historiography was built upon - that is, that history is a science, with verifiable facts and objective truths. It's not. And that's okay.

There was an interesting thread a month ago, where the question of why we study history was put forward. The answer rarely was to map out our past or anything like that. I personally prefer the top-voted answer:

If you think that learning from other people is a worthwhile endeavor, then you should realize that most people are dead now, and you must turn to history to consult them. To me, history isn't necessarily about improving military decisions, or making better political choices. (Though it can inform those things.) It's about understanding who we are and where we came from, and learning from other people about who they were and what they cared about. Learning other ways of doing things can open up new avenues of thought that wouldn't have otherwise occurred to us. It can help us understand and respect other ways of doing things, and to value our own culture and beliefs. And to me, that's worthwhile.

Related to this is the thought that history is essentially the study of humanity. It's an identity-forming process. We project ourselves onto the past and study our own reflection - this in itself is a realisation we got from postmodernism. And by looking at ourselves, we don't just learn more about ourselves, but we form an identity as well. History is at the same time a mirror and a canvas on which we paint ourselves.

It seems to me that your existential crisis is about the methodology of history, instead of about its purpose. Because, in some way, you still hold on to the traditional purpose of history and now that postmodernism has undermined the traditional methodology that goes with it, you feel lost. But you'll find that postmodern methodology goes best with a postmodern purpose of history - it may be the one I outlined here, it may be one you find yourself. In any case, there's no need to despair yet. History still has value.

I have a thorough dislike of postmodernism; it is too extreme for me. Postmodernism basically does away with the idea that language reflects reality. If language is indeterminate, if we can't be sure what it refers to (if anything), if all we do with language is construct our own reality - then language would be useless. We know from experience that it isn't. John Tosh in The Pursuit of History puts it like this:

Historians frequently acknowledge that they cannot fathom all the levels of meaning contained in their documents. But to maintain that no text from the past can be read as an accurate reflection of something outside itself flies in the face of common experience. In a set of trade figures or a census return the relation between text and reality is palpable (which is not to say that it is necessarily accurate). A carefully considered literary production such as an autobiography or a political tract disguised as a sermon presents much more complex problems, but it is still important to recognize that their authors were attempting a real engagement with their readers, and to get as close as we can to the spirit of that engagement.

Furthermore, the postmodernist denial of (knowledge of) causality of events is too extreme for me. I accept that causality in history is not as clear-cut as causality in physics, but I would not dismiss every attempt at identifying causality as mere interpretation. In at least some cases we certainly can say that some event A contributed to some event B happening. Would B have happened without A? Who knows. If something like A happens again, will something like B happen again? Probably not. But damn me if A didn't contribute to B happening.

All that said, what I would agree with, is that it is impossible to get to 'The Truth' in history. There is so much from history that is lost to us that we can never get a complete and accurate view of history. Because our view is at best fragmentary, any Rankean attempt at history is doomed to fail. As has been said by others, history's benefit to us is mostly limited to gaining an understanding of ourselves and our society.

You're not alone in what you're going through - I've spent years wrestling with these questions, as has most of the rest of my PhD cohort. You can come out the other side if you keep pushing forward! :)

Like many of the other commenters here, I've come to appreciate postmodernism more and more as I understand its implications better. It does kill the kind of certainty we wanted to find in the past when we first started studying history, but once you get past the nihilistic despair that inevitably accompanies that realization, a lot of exciting possibilities open up. Postmodern historians can never hope to write the True History of All Things, but that's ok because we can do other things that (I think) are much more interesting.

Postmodernism boils down to the proposition that everything's a story - 'facts' are constructed, and are then woven together into narratives by people, power structures, discourses, etc. But at their root, they're all just competing stories about how the world is, and we - living today - get to build our world out of the stories that we're told and the stories that we write about the world now. As historians, we've chosen to write stories for the present based on the past, and to do it in such a way that the past can be allowed to come to life and change us and the way we think about the world. We open ourselves up to old stories, and we see where those stories take us, and how we can arrange them to make sense of them and the world they came from.

An example. Late antique (the end of the Roman empire) historians studying the 'barbarians' who migrated into the western Roman empire would pull out a late Roman historian (like Ammianus), find all the references to the barbarians, and treat these as 'facts' to be reassembled into a comprehensive history of What Happened (for an example of this, look at H. Wolfram's History of the Goths, 1980). The 'facts' might be biased or inaccurate, so historians of this school tried to sort them into good and bad pieces of data, but in the end, the idea was that they could be cut out of their original sources and sewn back together into a thick, Frankenstein's-monster-esque summary of the data.

Postmodernism has completely changed this by causing historians of this period to see their sources, first and foremost, as literary works - as stories, complete with plots, themes, literary structures, and complex agendas. You can't chop up a work of literature for 'facts' without first considering how all of its pieces fit together in the larger structure that the author was building to make his larger point (if you pull out the facts you want without considering their context, you're likely to miss the reasons the author put them there, and without understanding those reasons, you can't really understand why the author constructed these 'facts' the way he did). So, instead of writing massive compilations and analyses of data, historians of this material are now looking at the stories late antique authors were telling in their contexts, and using this to write a better story for ourselves about their world.

The results are both more interesting, and more in line with the nature of the historical data itself. Because most of the texts historians use aren't data - they're stories. And when we treat stories as data, we're pushing them into a box that limits and distorts what we can get out of them, and what they can say to us. Postmodernism frees us to read things as stories instead of facts, and this has (at least in my field: late antiquity / early middle ages) opened a wealth of new avenues for fantastic scholarship.

And in the end, we base our stories about the past on evidence, and that evidence speaks with its own voice. It will change and challenge our perspectives if we pay enough attention to it. That's what keeps us from writing pure fiction, and it's what makes the task worth continuing.

I have also gone through this phase and recognized the validity of the postmodernist critique. My conclusion is pretty simple.

1 As a historian I should act as if the "truth" is recoverable. Even if it's impossible, even if there's no ONE "truth," that doesn't mean that I should just give up trying to understand the past as accurately as possible. That would be the dividing line between what I do as a historian and a historical novelist.

2 Once I realized this, I became more open minded with other people's writings of history, as long as they too are respecting the evidences from the past. This opened my eyes to previously unacknowledged narratives of the past. (In my particular case, I used to ignore Marxist historical writings as crap until I went to grad school).