1. People are born with certain rights that cannot be taken away. These rights are: being alive, not being slaves, and able to make their own choices.
2. Liberalism, the idea that humans have natural, inherent rights.
3. John Locke. His ideas are most fully developed in his Second Treatise Concerning Civil Government. There, he uses the phrase "life, liberty, and property", which Thomas Jefferson edited a bit when writing the Declatation.
This isn't in paragraph form, but I assume you can do that on your own ;)