It is inhumane to declaw cats. It mutilates them for the rest of their lives and does not allow them to live as they were intended; they can no longer walk without pain or discomfort, they cannot protect themselves, and the procedure is painful. It is equivalent to cutting off the third joint on all of your fingers. It actually causes more problems than it solves because the cats become more aggressive, use furniture instead of a litter box, and have behavioral issues as documented by the CVMA in their journal.
To learn more, you can visit the Paw Project at pawproject.org.