I was very lucky to attend one of Putnam's seminars at Uni abot logic and necessity. His in depth understanding of mathematics, physics, biology and many other sciences made him an almost ideal critic. I was impressed by how, when challenged, he was always able to restate his arguments based on stronger, more fundamental assumption. Putnam is a pleasure to read (which is not always the case when it comes to philosophers) and addresses many of the topics that occasionally come up on hacker news. Can't recommend him enough.
