Punctuation

Hello, everyone. I am struggling to understand how does punctuation works. While I know some rules for this. But while reading New York Times book review I came about a paragraph. Please tell me how the
"Comma" is used in this whole paragraph. And from where and how can i learn this type of Punctuation. Any link or book which is a self teach based.
Here is the paragraph:
They were, in my view, not caused by the ordinary negative human sentiments, as Spinoza called them—fear, greed, tribal hatreds, jealousy, love of power—though of course these have played their wicked part. They have been caused, in our time, by ideas; or rather, by one particular idea. It is paradoxical that Karl Marx, who played down the importance of ideas in comparison with impersonal social and economic forces, should, by his writings, have caused the transformation of the twentieth century, both in the direction of what he wanted and, by reaction, against it. The German poet Heine, in one of his famous writings, told us not to underestimate the quiet philosopher sitting in his study; if Kant had not undone theology, he declared, Robespierre might not have cut off the head of the King of France.