The correct answer to this open question is the following.
I am going to choose the First Amendment to the United States Constitution.
The three specific arguments in favor of why this Amendment is necessary in a democratic society are the following.
1.- One of the most important characteristics of modern democratic societies is that citizens are free. Without freedom, there is no democracy.
2.- People have their own set of belief systems and they will always have them. It is intrinsic to human nature. No matter what religion people profess, it is their right.
3.- The right to assemble in a peaceful way to exchange ideas, no matter what kind of ideas, it's part of any democratic government and society in the world.
The two arguments against why this Amendment may no longer be necessary in today's America.
1.- It is so implicit that citizens have rights that will come a day in which this value of liberty would have no need to be part of a Bill of Rights.
2.- Science and the use of logic could be a substitute for the ingraining belief that people need religion to have something to believe in. When science could be able to explain it all through the use of reason, maybe there won't be the necessity to include freedom of religion as part of the Bill of Rights.
