There is a condensed version of Pais' life story in his Wikipedia entry. He grew up in Holland, completing his graduate studies under Uhlenbeck in 1941 (see below). He survived the war in hiding in Amsterdam (not far from Anne Frank) and eventually immigrated to the US, becoming a member of the Institute for Advanced Study.
Here is Pais' recollection of how he became of student of Uhlenbeck's (p.31). Amazingly, I had the same experience, and so have all of my students ;-)
I ... told Uhlenbeck of my hopes to become a graduate student in theoretical physics under his guidance.
Uhlenbeck's response was unexpected. "If you like physics," he asked, "why don't you become an experimentalist? Or if you like mathematical aspects of theoretical physics, why not become a mathematician?" In explanation he noted that the practical future of a theoretical physicist in the Netherlands was extremely limited. At that time there were only five professoriates in the whole country. ... [more dissuasion] ... Furthermore, he added, theoretical physics is very difficult, it would be a life of toil with many frustrations and disappointments.
I was quite taken aback and mumbled, "But I like theoretical physics so much." Uhlenbeck's reaction was again unexpected. "If that is really true," he said, "then by all means become a theorist; it is the most wonderful subject you can imagine." As he later told me, his preliminary attempts at dissuasion were exactly like those he himself had been exposed to when he wanted to start his own graduate studies, adding that he used the same routine whenever anyone applied to study with him.
...Years later I told Uhlenbeck how that first afternoon with him had affected me. He told me with a smile that he had gone through the very same treatment, had the very same reactions, when he had visited his revered teacher, Paul Ehrenfest, for the first time. Ehrenfest in turn had received the same treatment from the great Ludwig Boltzmann in Vienna. This tradition is part of teaching in the grand old style, concentrating on but very few students. In my time I was the only student Uhlenbeck had taken on. Because of that privilege I may count myself as a spiritual great-grandson of Boltzmann. Meanwhile the old style has gone forever, I think, because of the large number of students now clamoring for higher education.
Pais wrote some important papers with Gell-Mann, including ones on Kaon oscillations and Strangeness. The result on Kaon oscillations, despite being a simple exercise in elementary two-state quantum mechanics, was not accepted by other theorists (the reactions of Racah and Dyson are recounted) until verified experimentally! (p.338: In 1956 a Columbia experimental group reported that the "rather startling properties of [neutral K's] ... predicted by Gell-Mann and Pais ... have been confirmed" :-)
Later Pais and Gell-Mann had a falling out, and Gell-Mann's hostility caused Pais some distress. In the memoir he describes reading the following inscription in St. Paul's church in Baltimore, which he liked very much (p.339).
Go placidly amid the noise and haste and remember what peace there may be in silence. As far as possible without surrender, be at peace with all persons.
Speak your truth quietly and clearly, and listen to others, even to the dull and ignorant; they too have their story. Avoid loud and aggressive persons; they are vexatious to the spirit.
If you compare yourself to others, you may become vain or bitter, for always there will be greater or lesser persons than yourself. Enjoy your achievements as well as your plans. Keep interested in your own career, however humble; it is a real possession in the changing fortunes of time.
Exercise caution in your business affairs, for the world is full of trickery. But let this not blind you to what virtue there is; many persons strive for high ideals, and everywhere life is full of heroism.
-- Max Ehrmann