Some time ago in college we looked at the evidence for functionalism and intentionalism and there was hardly any evidence showing that Hitler planed it and decided on what was happening with the extermination of Jews. Is it just the fault of my lecturer or is there really only little evidence?
From my understanding, there is considerable debate as to what extent he was involved in the actual planning of the Holocaust, but basically no debate (minus the conspiracy theorists) that he and other Nazis had no role in it at all.
It is a debate between two groups called the functionalists and the intentionalists.
Functionalists argue that the structure of the German government, combined with the political atmosphere and the ideology Hitler crafted all together produced a genocidal policy, in which Hitler's intentions were secondary, while intentionalists claim that Hitler and other high-ranking Nazis sought out the genocide themselves and were directly behind it.
Here is what I believe to be a good piece on it:
http://eview.anu.edu.au/burgmann/issue2/pdf/ch06.pdf
According to the author (and several other historians) the evidence for Hitler's direct involvement are slim.
You may also be interested in this thread.