To quote Wikipedia because I agree with it, "rights are legal or moral entitlements or permissions."
"We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, "
The Wiki definition obviously disagrees with the Declaration of Independence. The founding principles of the United States include that rights are unalienable. They do not exist at the behest or by the creation of the state. They are an intangible creation from the rational minds of men intended to define the relationship of men to each other. Bear in mind that by this definition, rights do not apply in nature, only among men. Nature does not have a rational mind, therefore rights cannot apply.
To me, rights exist only because people agree to let them exist. Therefore, rights change over time, and they are indeed based on the beliefs of people. I don't think that there is a fundamental set of rights - to life or even to existence.
"that among these are Life, Liberty and the pursuit of Happiness. That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed"
The Declaration continues to explain that the purpose of government is to secure these rights, not to create or limit these rights. It's not so much that people let rights exist, but that rational men acknowledge they exist and have joined together to ensure that the benefits of these unalienable rights are protected.
Like it or not, agree or disagree, this is the philosophical principle that underlies the foundation of the United States. This is the basis of the freedoms you enjoy, the source of the constitutional protection you expect and the envy of citizens in nations around the world where governments deny these basic rights. In nations where rights are denied, it is not so much that these rights do not exist in the relations of rational men, but that irrational men are denying these rights to others, at least in the context of the founding principles of the United States, which BTW, is still a model for the world over 200 years later.
Two girls and a cup...cake