It is a fact, certified and true, that the very people who today are telling you how the MX missile is going to work are, at this approximate moment, unable to put up their own Christmas trees.

It is also a fact, both certifiable and true, that the very people who today are telling you about the efficacy of science, about Dense Pack and missile fratricide, are now taking out the boxes of Christmas lights they carefully put away a year ago, only to find that in the intervening time the strings of lights have intertwined all by themselves.

It is true, of course, that anyone who knows anything at all about the erecting and trimming of a Christmas tree knows the limits of science--not to mention the strains this puts on a marriage and how the very concept of sexual equality goes out the window when it comes time for a person (the man) to get under a tree and be told by another person (the woman) that the thing is not straight.

No one who has not been under a tree, a needle up his nose, his hands bleeding, his legs ensnarled in the tree stand, possibly can appreciate what a humbling experience this is. It is, in fact, an experience that has been shared by millions of people now for hundreds of years, with maybe just a few of them realizing that it is a metaphor for life: If something can go wrong, it will.

Let us first consider the lights. Not only do strands of them engage in wild and contorted sex during the months they are stored, but for no reason that science can possibly explain, they sometimes work when off the tree and not on. And as if that were not perplexing enough, they sometimes blink when they are not supposed to, or fail to work entirely, necessitating a search for the one bulb that has gone out.

It goes without saying that this often fruitless search for the bad bulb is conducted while perched high on a ladder, leaning out in a style reminiscent of a certain tower in Pisa, with one branch poking you under the arm and another threatening to take out an eye.

It goes without saying, also, that in reaching for the bulb, you knock off at least two glass ornaments, both of which shatter into a zillion razor-like pieces, and then you have to run to the store to find lights made in Japan that will not fit those made in Hong Kong or any made in Poland--none of which is the right color anyway.

Now we come to the tree itself. A tree that in the lot had the posture of a West Point plebe somehow contorts itself on the roof of the car and arrives home looking like the Hunchback of Notre Dame with pine needles. This means that it has to be inserted into the stand at a weird angle calculated to compensate for the warp but which, when viewed by a woman at a distance, only makes the problem worse.

But even before that, the tree has to be transported home. It has to be placed on the roof of the car, secured by ropes and and tied with knots learned from the Boy Scout handbook. On the drive home the tree will decide that it would be fun to inch forward on the roof and suddenly flop down to block the driver's view.

This is because the tree, officially and scientifically dead when cut weeks before, suddenly takes life after leaving the lot. It is perhaps most active when the time comes to enter the house. Then, suddenly, it does a wonderful imitation of a child refusing to leave for the first day of school. It squirms and it fights and it digs in its heels. It grabs at the door and anything else in sight, suddenly becomes wider and heavier than it was previously, and grows branches in places where they did not exist before. These it uses to tickle you in the face.

You would think that a country that has lots of experience with Christmas trees would approach the MX with humility. No such luck. The missiles will be built, trucked to the desert, placed in their stands and programmed to do all sorts of wonderful things. But when the button is pushed, probably nothing will happen. I sleep well, anyway, knowing that the Soviet missiles will do the same thing. They can ban Christmas trees, but not the lessons Christmas trees teach.