If you are discussing immigration with a friend, you are likely to hear him reflexively blurt out the gem: "this is a nation of immigrants." When he does, simply point out to him that eighty-five percent of the residents of the United States were born here.

How could that preponderance of homegrown Americans justify us being called a "nation of immigrants"?

Certainly we are descendants of immigrants (as is everyone in the world), but that is not the same thing as being an immigrant.

Anyway, such a statement is no justification for continued mass immigration. The inference that "We are a nation of immigrants and, therefore, we must not limit immigration" is a classic example of circular argument.

What is says is this: Because we are a nation of immigrants, we have to allow for massive immigration which, in turn, makes us a nation of immigrants. Hence its circularity.

Circular arguments are invalid in the logical sense by virtue of how they are structured and not what do they mean. They lead to faulty (and, therefore, useless) reasoning in which the thesis (the very thing which is to be proved) is used as a premise in its proof.

And circular arguments certainly do not form a good basis on which to formulate sound public policy.