One dramatic way to expose the fal sity of the most dangerous assumption of human history--that nuclear weap ons can be used to achieve a reason able purpose --would be to stage a nu clear test explosion.

Has President Reagan ever person ally witnessed the explosion of a nu clear weapon? Has President Brezhnev ever seen an atmospheric test of a nu clear weapon?

The United States and the Soviet Union agreed in 1963 not to conduct nuclear weapons tests in the atmos phere, outer space or under water. It would not be necessary, however, to negotiate an exception to the Limited Test Ban Treaty to demonstrate the awesomeness of weapons whose prolif eration man has not been able to con trol. France was not a party to the Limited Test Ban Treaty; it conducts several atmospheric t pests each year. Thus, the French could stage a test nu clear explosion in an environment en livened by buildings and animals and invite all heads of state (including those who aspire to become nuclear powers), media and others to witness firsthand the destruction these weap ons can wreak on mankind.

Can one imagine that heads of state and media representatives would re ject an invitation of the French gov ernment to witness firsthand a test of one of the 50,000 nuclear weapons now deployed in 24 countries and their de pendencies? If President Reagan de cided to witness his first nuclear weap ons explosion in the atmosphere, would President Brezhnev be far be hind?

Environmentalists and others will be disturbed by any atmospheric burst of a nuclear weapon. But testing a weapon in the air and having it wit nessed personally and by live televi sion the world over, would be more a spur to peace than continuation of the nuclear apathy to which mankind has become accustomed.