a.    Trying to prevent patents from being issued on inventions that a prior inventor has already placed in the public domain.
b.    Cost-Effective Choices: Want to make sure people make cost-effective choices in deciding to search existing technologies versus invent a new one. Patent system skews you towards inventing when close call btw that and search, so maybe we want to take patent system out of game when we want to encourage searching – preexisting stuff.
c.    Competitor Problem: If someone does it on their own, now have to worry that rivals will search for prior art to invalidate patent. Rival only looks after the fact. What do we allow competitor to do? Don’t want them searching just to invalidate other’s patent.