President Reagan's Strategic Defense Initiative (SDI) is financially and scientifically impractical, a representative of a pro-nuclear freeze movement told 65 Summer School students last night at the Kennedy School of Government.

"If you could show me that a nearly perfect system could be built, and that it would be cheaper than Soviet countermeasures, I'd buy it," said Paul Carlson, director of research for the pro-freeze Union of Concerned Scientists, which claims 100,000 donors.

Carlson said that SDI is likely to perpetuate the arms race because no shield system could possibly be effective enough to convince the U.S. to abandon its nuclear weapons. He also cited the Reagan administration's argument that SDI could be used to protect U.S. missile silos as proof that the program is more an aid than an end to the use of nuclear weapons.

"What I think is misleading is the idea that SDI would change the [nuclear deterrence] equation at all," said Carlson, the first guest of a political discussion series organized by Robert Mascola '86 as part of Harvard's "Summer in Boston" program for Summer School students.

The Union of Concerned Scientists advocates a U.S. research program that would prevent the Soviet Union from acquiring a technological advantage, but opposes physically building the proposed anti-missile system, Carlson said.

"Visions of Star Wars," a television feature critical of SDI, preceded the discussion.