Here is a defense of Donald Rumsfeld's tenure which runs contrary to the present conventional wisdom.

One value of hearings is that we may gradually get a better picture of the truth. How, exactly, did we come to dilute the Geneva Conventions? What was the process which led us to war with Iraq?

It may take decades for the truth to emerge. Oddly, historians may be handicapped by the lack of a paper trail. Emails are easy to destroy, and will likely have been cleared off the hard drives by then.

History is a never-ending debate. Only by weighing competing versions of what actually happened can the reader begin to get an accurate picture of what actually happened. Even then, it is likely that the conclusions will be clouded both by the writer's biases and the reader's subjectivity.

Some people view the study of history to be a social science. You study the facts, test your hypotheses, develop a theory, and then wait for that theory to be contested.

I find the social science model a bit sterile. I think history should be considered one of the Humanities. Historical truth is best captured by great writers, like Carl Sandburg and Winston Churchill, who have a talent for narrative and a big enough personality to transcend petty details.