Here is a short, great video of Tim Keller speaking on passion and entrepreneurship. Interestingly, he points out the the last of the seven deadly sins — sloth — doesn’t refer to laziness but rather passionless:
[vimeo http://www.vimeo.com/23636811 w=398&h=224]
In other words, living a life without passion was traditionally considered to be one of the seven deadly sins.