Smith drove a car than to say that Mr.

Smith drove a car than to say that Mr. Johnson never drove a car. To be truthful in the positive one, one needs to see Mr. Smith once driving a car. To say truthfully that Mr. Johnson never drove a car, one needs to know all the past of Mr. Johnson. Let us deal with a future information. We may predict that there will be, within fifty years, a genius scientist from among the people of Detroit. This is much easier than to say that there will be no genius scientist in Detroit within fifty years.