Intellectual curiousity is self-explanatory.
Intellectual discipline is harder to pin down. One aspect is avoiding
various extremes such as
(i) starting lots of projects but never completing any
(ii) only attempting do-able problems -- the next problem that suggests itself.
Another aspect is being able to formulate your own views on what is important and interesting while being aware of other people's views.
Commentary. I know you can think of counter-examples, but it's a generality, OK? My conclusion is that at age 45, say, you should reflect on what you want to achieve in the seond half of your career, not just continue on auto-pilot.
Commentary. Because they'll be around longer.
Commentary. Why indeed.
Commentary. Reminiscnt of a great quote from Don Knuth: email is great if you want to stay on top of things; But I want to get to the bottom of things!.