It is going to be so good to get President Reagan back to Washington, D.C. Not only will the city be brighter, he may be too.

Where many of its residents flee Washington in August to "get back in touch with reality," even if that reality is just a stretch of beach, this president pulls the plug on his contact with the real world as soon as he skips town.

Reagan, as everyone must know by now, is the living refutation of Francis Bacon's aphorism that "knowledge is power." Reagan has flourished in politics by demonstrating that "conviction is power." He knows what he thinks and has the power of his own beliefs. But he treats knowledge as if it were dangerous to his convictions. Often it is.

When someone approaches Reagan bearing information, he flees as if from the leper's touch. "Get away, kid, you bother me," is this president's response to memo-wielding aides. "You say you've got some new 3-by-5 cards for me? What's wrong with the old ones? They got me this far."

The occasion for all this sarcasm is the latest, but surely not the last, sorry display of presidential ignorance -- namely, the comments from the sky ranch on improving conditions in South Africa.

I don't know what is more discouraging: Reagan's lack of understanding or the convolutions of the people who work for him (and incidentally run our government) as they invent explanations and try to cover up for what he didn't know.

I have a good deal of sympathy for those people. How would you like to be explaining the terrifying prospects for South Africa and the difficult policy choices that situation poses for the United States to a man who believes that "they have eliminated the segregation that we once had in our own country . ."? That cannot be easy work.

The task of watering the arid desert between Reagan's ears is a challenging one for his aides, even when they have him pinned down in the White House and he can't hide. (I don't believe the songwriter had the Oval Office or Reagan in mind when he penned, "Run for the Roundhouse, Nelly, They Can't Corner You There.")

The briefing chore becomes impossible when he's off at the ranch, and it's evident no one even tries.

Ed Meese was probably the smart one when he decided, back in 1981, to let the vacationing Reagan sleep through the dogfight between the U.S. Navy planes and Libya's fighters, rather than disturb his rest in a Los Angeles hotel. From that time on, these trips home to California have been as nerve-wracking for the White House staff as they have been precious to Reagan.

A year ago, you may recall, the president was so relaxed out there that he tested the microphone for his weekly broadcast by saying, "My fellow Americans, I'm pleased to tell you today that I've signed legislation that will outlaw Russia forever. We begin bombing in five minutes."

That remark was clearly intended to be more humorous than his comments on South Africa, but the two betray a common pattern that is important to understand: at heart, Reagan is a man of his convictions, and those convictions never change.

They may be overlaid for a time, when aides manage to plug in enough real-world information so that Reagan recognizes it is impolitic to give voice to his inner thoughts. But he never abandons them.

Reagan, for instance, has never accepted the reality of racism. Just plain won't recognize it. He said at one point in his presidency that he was unaware of racism, growing up in a family that he says taught him to treat every person the same.

Many of us grew up in that same kind of family. But you would have to be a creature from another planet not to be aware of pervasive racism in the Midwest of his or my own youth.

But Reagan never recognized the reality. So, conveniently, he never had to acknowledge the importance of the struggle to overcome racism. He opposed the Civil Rights Act of 1964 and the California open-housing law. Even when he was persuaded before the 1984 election to sign the bill commemorating Martin Luther King Jr.'s birthday, he could not resist making a wisecrack about King, for which he apologized to his widow.

So it really was not surprising that as soon as his advisers stopped reminding him that the South African regime was racist, Reagan reverted to form and declared it "reformist."

That is so typical. Reagan always is inclined to put his ideology ahead of any contrary information, because his ideology is comfortable, and information often is not. Inside the White House, there is a constant battle between those who want to supply Reagan with real-world information and those who prefer to reinforce his comfortable ideology. When Reagan is in Washington, there is a chance that information will win out; when he's away, ideology always prevails.

So, welcome back, Mr. President, to Washington and the real world.