Of all fields of historical enquiry, Germany’s Third Reich is perhaps the richest in sources and historiography. Therefore, it is logical to assume that this is where we see history done at its best. The chief interest of this dissertation is how historians select their sources and how they use the evidence they find in their sources. I have taken relations between Jewish Germans and non-Jewish Germans as a case study because of the enormous quantity of primary source material and because so many historians have commented on the issue. I do not attempt to make any claims about what happened between Jewish Germans and their non-Jewish compatriots nor do I make a moral assessment of behaviours and attitudes among the ‘ordinary’ people of Germany under the Third Reich. Rather, this is a technical exercise to examine how well the historians have done history in this particular area. My systematic review of the historians’ methodologies reveals that many either distort the evidence they cite or put forward arguments that go well beyond what the evidence warrants, perhaps because of pre-conceived theories which shape their approaches to the evidence. Moreover, they fail to make the best possible use of some types of source such as personal narratives. In order to ascertain whether these sources can be better used, I systematically analyse a selection of personal narratives which are sometimes quoted by historians, in particular the 1933-1945 diaries of Victor Klemperer. My question is: Do these testimonies really say what the historians claim they say about relations between Jewish and non-Jewish Germans? And if not, how can we analyse them to determine what they actually do say? The two kinds of problems which emerge are how to select a balanced range of sources and how to use them properly. My argument is that there are six methodological principles that should underpin good historical practice. Because historians are not scrupulous to apply these common-sense rules, their arguments are methodologically flawed and they do not use some sources to the full extent of their value. This raises the question of whether these problems are confined to this particular field or whether they are endemic to the history profession as a whole.