 How does the writer use twins in their argument?
It's an easy way to show sound-bite leadership on an issue that everybody is talking about, without much risk of bitter consequences. He also openly claims the authority to decide how people reproduce. What law or principle--secular, humanist, or religious--says that one combination of genetic material in a flask is OK, but another is not? About one in every 1,000 births results in a pair of babies with the same DNA. Scientific studies on such twins--reared together or apart--show that they share many characteristics. Despite how many or how few individual characteristics twins--or other clones--have in common, they are different people in the most fundamental sense . They have their own identities, their own thoughts, and their own rights.
 They show that clones already exist, and are proven to grow as individuals and have their own individual rights.
 They show that clones already exist, and are proven to grow as individuals and have their own individual rights.  They show that like twins, clones use the same DNA to make people with shared characteristics.  They use twins to show that if clones did exist, they would grow up the same way that twins do.  They show that twins are a common occurrence, meaning cloning would not be such a new concept to introduce.