Of the four project development variables - scope, cost, time and quality - quality isn't really a free variable. The only possible values are "excellent" and "insanely excellent", depending on whether lives are at stake.
Kent BeckResponsible Development shares many practices with XP but the roots are different. Responsible Development's values are honesty, transparency, accountability and responsibility. These lead me to pairing, test-first, incremental design, continuous integration and so on because they support the values.
Kent BeckI've known people who have not mastered their tools who are good programmers, but not a tool master who remained a mediocre programmer.
Kent BeckI don't like the feeling, but I've got to say that a little fear makes me a more focused, more responsible programmer.
Kent Beck