My dynamics professor mentioned to me that most of the physics world considered themselves to have conquered human knowledge at the end of the 19th century. The famous apocryphal quote from the head of the patent office saying that everything that could have been invented, had, comes to mind. (http://patentlyo.com/patent/2011/01/tracing-the-quote-everyt...)
I found out from another professor that the first had actually wanted to go into physics in his young life, but was encouraged to get into engineering, since hard science had basically been played out. Of course, the early 20th century took off, and we have the classic picture of Einstein seated with all the other great scientists of the day. This is the group my prof could have rubbed shoulders with, and he was apparently a little bitter about it. I probably would have been too.
High point of human civilization? You mean colonialism in its full force, blatant exploitation, racism, etc was its high point? I'll take Europe today over 1909.
Not the OP, but I think that was the high point of the particular European centric civilization that came out of the Enlightenment. There will be other high points for sure, but each will come when their own civilizations reach maturity.
And no, nobody alive today will see one of those, it is too late in the previous cycle and too early in the next one for that. But you can make the next one happen today by mastering something worthy and passing it on to the next (human) generation. There's people not yet born who will use that as raw material to create stuff that we would not be able to understand even if it hit us in the nose.
I think he means zenith, not nadir. 1909 was the high point of human civilisation, before barbarism and ugliness took hold.
Also, not covering Freud, Nietzsche & Marx was no mistake: this is a collection of lessons to learn, not lessons to learn from.