Purring would seem to be in her case an automatic safety valve device for dealing with happiness overflow.

While Free Choice Vouchers didn't fulfill my vision of a health care system in which every American would be empowered to hire and fire their insurance company they were a foothold for choice and competition and a safety valve for Americans whose employers are already forcing them to bear more and more of their family's health insurance costs.

I don't believe in life after death. But I do believe in some grinding destiny that watches over us on earth. If I didn't the safety valve would give and the boiler would explode.