At the beginning, he would enumerate five of his favorite talks, said that Andy Strominger's vision talk brought Gross almost to tears, and he finally concentrated on the explanations why the people in that Princeton room have faith in the theory despite some outsiders' opinions that they shouldn't.
(Paul Steinhardt, a speaker at Strings 2014 who has delivered some "strange" statements to the audience, was chosen as the only named prototype of the critics.)
String theory is a framework, not a specific theory making specific down-to-earth predictions about realistically doable or ongoing experiments that could decide about its fate, but David Gross recommended a very intelligent 2013 book by Richard Dawid, a trained physicist and a philosopher, that articulates rather nicely what the actual reasons for the competent physicists' faith in the theory are in the absence of those confirmed new down-to-earth predictions.
Incidentally, the rating and ranking of Dawid's book at amazon.com is catastrophic, especially if you compare them with some of the anti-physics tirades – a big enough piece of evidence that most laymen are just way too stupid and superficial regardless of the time some people are spending with licking these laymen's rectums. The rank that is worse than 1 million also indicates that no listener of Gross' talk has bought the book via amazon.com.
The three arguments that either instinctively or knowingly contribute to the competent physicists' faith and growing confidence in string theory are
- UEA: unexpected explanatory coherence argument. If the theory weren't worth studying, it would probably almost never lead to unexpected answers, explanations, and ways to solve problems previously thought to be independent
- NAA: no alternative argument. There's no other game in town. The argument has existed in the case of the Standard Model – in recent decades, NAA was getting increasingly important.
- MIA: meta inductive argument. String theory is a part of the same research program that includes theories whose success has already been established.
At the end, David Gross presented his theory of history that was especially addressed to the physicists who ever get depressed about anything. Things are always getting worse. But we know that in the long run, things are getting better. Why is it? The idea of Gross' explanation is more or less mathematically isomorphic to the "escalator", a meme about "how skeptics describe the temperature" and "what the temperature is actually doing" promoted by climate alarmist John Cook:
You see that the first derivative of the temperature is negative – the weather seems to be getting worse all the time. (The summer 2014 in Czechia has been said to be over, too.) But if you adopt these smooth monotonic decreasing pieces of the function, there are discontinuities, often or mostly positive ones, so the weather is getting better in the long run (it's sometimes called the global warming). Gross has applied the same idea to all of history. Things are getting worse but suddenly Jump, a big improvement.
Of course, Gross has made some sign errors – he counted the 2008 U.S. elections as an improvement, for example – but his overall performance was pretty good.
Unlike his predecessor and his spouse, Barack Obama doesn't even know what to do with a bucket of ice water.