The following text has been expanded slightly from a lecture read at the Technological University Delft on 21 April 2006. As is often the case, there were certain difficulties with transforming a text composed for oral delivery to one written for publication. One can employ a more dramatic phrasing in person, with body language and personal interactions to qualify it, than it would be appropriate to use when the same text takes printed form. I have nevertheless left some of oral phrasing in tact, with an appeal to readers to give the text as a charitable an interpretation as they can. There are also always desires to make a printed text more complete than what might be necessary in an oral presentation. Although I have made some modest elaborations here and there and added notes, I have also resisted trying to go as far as I would like in this regard. The recurring “I” in the present version also bothers me to some extent, but to have become more scholarly would have imposed a kind of artifice if not a false image of detachment.