PreambleWe the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.
The Preamble of the Constitution says "We the People of the United States, in Order to... secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America."
There is your constitutional definition of natural-born citizen right there at the beginning of the Constitution: "...ourselves [We the People] and our Posterity [future children]."
Natural born citizens are the children born of We the People, for whom the Constitution was ordained and established to secure. How else would they "secure the Blessings of Liberty" except by limiting the qualification for the highest office in the land to the citizen children of citizen parents?
Posterity means our children and our children's children.
The Constitution was ordained and established to secure the blessings of liberty to our children, their children, and their children's children, and so on and on.
Article II Section 1 Clause 5 codifies it.
-PJ
If you just could have convinced any court in America, at any level of the judiciary or any Republican Chair of a committee of the House of Representatives to adopt your view, Barack Obama might not have been approved for the ballot by the Chief Elections Officers (usually a Secretary of State) of every state in the Union, twice.
As it stands now, Barack Obama’s mother, having been born in Wichita, Kansas to parents born in Wichita and Peru, Kansas respectively was enough to secure the blessings of liberty to her and her posterity.
The CURRENT law of the land defines a “Citizen of the United States at Birth:” http://www.law.cornell.edu/uscode/text/8/1401