Citizenship: A Top 10 List.

7. But how do we make good political choices when so many different issues are so important and complex? The first principle of Christian social thought is: Don’t deliberately kill the innocent, and don’t collude in allowing somebody else to do it. The right to life is the foundation of every other human right. The reason the abortion issue is so foundational is not because Catholics love little babies—although we certainly do—but because revoking the personhood of unborn children makes every other definition of personhood and human rights politically contingent.

From Archbishop's Charles Chaput's 10 principles for faithful Catholic citizenship.