One more thought: if you are interested in twentieth century analytic philosophy, Scott Soames' two-volume history provides clear and reasonably reliable interpretations of the history of some of the movements within that tradition.

Even though Soames does not provide a full or completely satisfactory history of analytic philosophy--his central narrative focuses narrowly on those treatments of the analytic/synthetic, necessary/contingent, and apriori/aposteriori distinctions that are most closely connected to Saul Kripke's celebrated work in Naming and Necessity, and the emphasis he places on the historical significance of Kripke's achievements creates some some significant gaps and oversimplifications--these texts are extremely engaging and reading them can be a good way to gain sophisticated introductory knowledge about some vital figures in recent philosophical history:

Soames, Scott, Philosophical Analysis in the Twentieth Century, Volume 1: The Dawn of Analysis. (Princeton, NJ: Princeton University Press, 2003) http://books.google.com/books?id=sS_lToqtGrIC&pgis=1.

Soames, Scott, Philosophical Analysis in the Twentieth Century, Volume 2: The Age of Meaning. (Princeton, NJ: Princeton University Press, 2005) http://books.google.com/books?id=M5umcZlECGQC&pgis=1.

Of the three histories listed so far, my assessment is that Russell's is the least reliable (but most fun to read), Kenny's is the most reliable and employs the best historiography (and so is the best elementary introduction to many Western philosophical traditions), and Soames offers the most sophisticated discussion of a much more limited range of figures and themes.

Russell's book is lively, but not that reliable. The best one-volume history of philosophy I've found is A Brief History of Western Philosophy by Anthony Kenny, which is accessible but sophisticated and concise yet comprehensive.

Unlike Russell, Kenny develops develop a sophisticated historiography that draws helpfully from wider cultural and historical events and trends. This gives his text a much more interestingly nuanced view than is normal in introductory histories of philosophy.

The book is entertaining and deeply informative -- and I consider it the very best of its genre! Here's an Amazon link (note -- the text I have mind is the one published by Blackwell in 1998; Kenny has published other histories of philosophy since then that I don't like as much):

http://www.amazon.com/Brief-History-Western-Philosophy/dp/0631201327

Bertrand Russell's History of Western Philosophy immediately comes to mind.

There is a number of different issues here. Let me comment on just one of them. We may indeed wonder how people, in certain situations, can come to act in appalling ways. The question as asked perhaps suggests that arm-chair philosophy might help in understanding this. But not so. This "how come?" question is an empirical one. What is needed is e.g. a knowledge of empirical work in social psychology, such as the Milgram experiment, which explored the willingness of subjects to inflict (apparent) suffering at the behest of an authoritative figure. The results of such work are highly alarming but also, I take it, highly salient for the historian. For they suggest something of the ready possibility of authority structures that might facilitate widespread evil behaviour. We can oh-so-easily be led to do terrible things.

Thank you for your question. I can't hope to answer it at all comprehensively. Instead I'll try to give a smattering of highlights, and some pointers as to where you might look to learn more. Among the questions that philosophers tried to answer at this time were: '

What is it to be virtuous, and can virtue be taught?

What is the soul, and does it survive the destruction of the body?

What is the best organization for a society to follow in order to be just?

What, at the most fundamental level, is the physical world made of? (Proffered answers included fire, water, and atoms.)

In what sense, if any, might the future be "real"?

There are lots of others. For a rewarding discussion that puts philosophical inquiry into a broader social and historical context, I would strongly suggest the classic _The Greeks_ by H.D. Kitto. Once you've gone through that, you can't go wrong by looking at some dialogues by Plato, in which the author purports to report various discussions his teacher Socrates had with his friends before being put to death by his fellow Athenians. See for instance Plato's _Five Dialogues_, translated by J. Cooper, and published by Hackett Publishing Co.

I think you raise one of the strongest objections possible to relativism, one so strong that it renders relativism impossible to formulate in that way (i.e., "All truths are relative"). But I do warn you that things get stickier as your get into relativistic theories. What makes them compelling? Here are a couple of general strategies that I've run across.

1. Negative Proof: Negatively, non-relativistic theories of truth seem, at least in the view of many, to have irresolveable problems of their own, arguably greater problems. So, if non-relativistic theories can't be right, some kind of relativism must be correct.

2. Positive Proof: Positively but indirectly, relativism seems (1) to answer serveral questions about the way the meaning of language and the designation "true" is determined and correlatively (2) it seems to be the consequence of investigations into matters concerning topics like whether a body of evidence can determine only one conclusion (answer: no), whether a word can have a single, clear, univocal meaning (nope), whether hypotheses are testable individually (no again), and whether any unique sentence or set of sentences can represent independent reality (no way). Then, of course, there seems to be the facts of sociology and history that exhibit countless and forever changing truth-claims.

3. Shown, Not Said. Some who are influenced by Wittgenstein, might argue that something like relativism can be "shown" by certain manipulations of language usages and certain investigations into the way language works, but it can't be proven. So, if you don't see the relativism, look again, look harder.

4. Biting the Bullet. Some might just embrace the idea that relativism is relative, too. Of course, that would seem to make it impossible for the relativist to criticize absolutists or to assert that absolutism is wrong (after all the absolutists might just say that, "well, absolutism is true for me or for my society, and that's supposed to be enough for you"). But watch it here. The relativist might then try to bring the absolutist to change her or his mind and accept relativism--but NOT by maintaining that relativism is "true" (where there can only be one truth or perhaps where truth is thought somehow to depict "the way things are") but by maintaing that relativism seems to be morally or politically preferable, that it seems more felicitous, the best explanation for our present social purposes, that it seems to work better, that it yields more pleasant consequences, that it produces more agreement, etc.

So, while you're right that relativism of the form you describe hoists itself on its own petard (as Schick & Vaugh like to say) and therefore is self-defeating, don't assume that all relativists would formulate their positions in just that way--at least not without a fuss.

I agree with Peter that one need to specify exact criteria for progress before making the sort of assessment that you describe. All such critiera and assessments will be controversial because our knowledge of ourselves and our histories is limited and controversial, but this by no way means that producing and rationally defending such assessments is worthless -- on the contrary, they can be extremely useful and interesting.

The political theorist George Kateb provides an interesting--and fascinating--example of how to assess human progress in the modern age. In his recent collection of essays. Patriotism and Other Mistakes (Yale University Press, 2006), Kateb assesses human progresses on the basis of a richly sophistcated conception of human and argues that the United States Constitution represents a significant achievement in the support of human dignity, which he defines (again, in a richly sophisticated and fascinating way) in terms of rights-based individualism. While Kateb's criteria for progress and assessments are certainly "qualified" in some of the senses that Peter has described, they are also impressive scholarly achievementsthat provide meaningful insight and information.

Kateb's discussion about ways in which current domestic and foreign policies and actions of the United States jeporadize this progress is also instructive: human progress is contingent, both in the sense that whever progress has occurred need not have occurred and in the sense that progress we have atained we can lose. So, although I am not at all skeptical about the possibility of crafting useful assessments of human progress, I am skeptical that there is a single, inevitable, univocal story to be told about human progress: there are many possible stories to be told, with many twists and reversals, and no easy lessons or morals about human progress simpliciter. So, conceptions of human progress as inevitably following one secure path (as, for example, in the political philosophies of Hegel and Marx and as in some religous texts) aren't plausible.

There can be no simple, unqualified, unequivocal "progress" in human history because what is to count as progress or regress must be determined as such by some measure, some set of criteria for progress. But, so far as I can seen, anyway, there is no unqualified set of criteria to measure by. One can, however, speak meaningfully about specific kinds of progress. For example, one can speak of technological progress in processor speed, or progress in understanding black holes, or in eliminating poverty, or in curing lung cancer, or in reaching the end of a journey, or in gaining financial independence. Mere "progress" itself, however, seems to have little meaning. About whether or not we remain "essentially the same" across space and time, I think the answer depends upon what you mean by "essentially." For myself, I think of people as plastic but not infinitely plastic. Just as one can make many different kinds of things with clay (even an infinite number of different things), one can't make anything. The physics of clay just won't permit everything. Similarly, while many different kinds of human being are possible (even an infinite number of different people), not anything is possible for us.

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

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"?