Back in the days when he was a novice governor of California, Ronald Reagan was often accused of being "too simplistic," shorthand for saying he was an actor who knew next to nothing about the complexities of governance.

As he so often does, Reagan turned the criticism back on his critics. His rejoinder was that "there are simple answers, just not easy ones" -- also shorthand. It meant that the problems of government are not as complex as they seem and can be solved by any outsider courageous enough to make tough decisions.

Reagan, who had genuine political gifts and the sense to bill himself as a "citizen-politician," carried the day with his counterattack. Americans, including this one, who would not knowingly patronize an unlicensed physician or fly with an unqualified pilot, tend to share the delusion that anyone can manage a baseball team or run the country. Before long, Reagan's simple-mindedness became the envy of politicians he bested.

Now the issue has been raised anew, by Reagan's conduct rather than his critics. In recent weeks, he has dismayed even supporters by an insistence on the most simplistic variants of two of the most complicated issues of his presidency.

Reagan's Strategic Defense Initiative, discussed often in this space, is a serious proposal. "Star Wars," as a Time magazine article termed it months before Sen. Edward M. Kennedy (D-Mass.) used the phrase pejoratively, is based on the sensible, if scary, proposition that someone sooner or later is likely to fire a nuclear weapon in calculation or anger.

The idea of a missile defense that would prevent a superpower from being held hostage by a fanatic government or that would protect U.S. missile sites and discourage a Soviet first strike is worthy of consideration and, arguably, implementation.

Unfortunately, Reagan's missile defense, which in his words would enable Americans and Soviets to "escape the prison of mutual terror," exists only in his imagination. Not even the most enthusiastic supporter believes that a space shield that would reliably protect civilians from nuclear destruction is technologically probable within this century.

Reagan's simplistic approach to one of the most complex issues of our time enables him to make the mental leap from fantasy to reality. He talks not as if strategic defense were a sensible goal, which it well may be, but a scientific reality.

A glimpse of Reagan's mindset was provided last week by Italian Prime Minister Bettino Craxi, a supporter of strategic defense, after he met with Reagan in New York. "He described a world completely defended by space shields in such a way that the threat of nuclear war would be completely eliminated," Craxi said.

Star Wars is not Reagan's only fantasy. Its earthbound counterpart is the Gramm-Rudman-Hollings deficit-reduction bill, which has been endorsed by the president and demonstrates that he does not have a monopoly on simplistic answers to difficult problems.

This legislation, like Star Wars, has a sensible goal: reducing looming deficits that mortgage the future of our children. It is also, as we used to say on the police beat, a confession. It confesses that neither Democrats nor Republicans are willing to confront deficits on their own and mandates that Congress and the president do what each already has the power to accomplish.

Gramm-Rudman, like Star Wars, places its trust in a magic mechanism. If the president and Congress cannot obtain deficit-reduction goals, the bill would leave Reagan with the dreaded alternative of dismembering his defense budget or raising taxes in order to balance the budget. Whatever the choice, he could blame it on the mechanism that he has helped set in motion.

Reagan is a president with attractive qualities -- solid values, many reasonable goals and a sense of what he wants to accomplish. But those who feared his simplistic approach had reason to worry.

Some problems have neither simple answers nor easy ones. Reagan's failure to understand this threatens the success of his presidency.

Reaganism of the Week: Telling an Indian journalist about his only stop in India, Reagan said: "My only experience in your country was one in which I wasn't even aware of it. I was on a flight from Taiwan to London and . . . the plane dropped in New Delhi for refueling and I was sound asleep, so at least I slept a few moments in India."