Our national problem is that liberals launch attacks on the MX, and conservatives don't like Midgetman. Neither pays much attention to how we can deal with the vulnerability of land-based missiles -- which is what drives MX and Midgetman.

It's a debate of negatives. Critics are rarely forced to say what they would do differently. That offends ideologues of both right and left. But unfortunately national security doesn't fit neatly into the tight ideological pockets of either the right or left.

In a rational world, we ought to say, "Okay, if you don't like this MX basing mode, what is your method for dealing with ICBM vulnerability? If you don't like the single-warhead Midgetman, what is your alternative? If you don't like the Scowcroft Commission recommendations because you don't like MX in silos, or you don't trust the Reagan administration to conduct the arms control talks correctly, what is your alternative?"

Opponents should not be allowed to walk away from the underlying issue. The loyal opposition in a democratic system has the responsibility to offer alternatives with its brickbats.

And solving the land-based missile vulnerability problem is what it is all about. If the Scowcroft solution falls apart either because of attacks by the left on MX or attacks by the right on Midgetman, we will have to try some other approach. Having thought of two solutions -- the Carter proposal and Scowcroft -- it should not be beyond the wit of man to come up with a third.