The Post's Sept. 27 editorial on David Souter {"Yes to Judge Souter"} painted judicial restraint as an ''abstract theory'' and activism as ''the fluid need 'to make the Constitution a reality for our time.' '' No matter what the truth behind these ''caricatures,'' they obscure the deeper issue of checks and balances within the Constitution.

The heart of the issue is summed up in two of the quotes The Post chose to buttress its support. I refer to Judge Souter's acceptance of an ''unenumerated right of privacy'' and his view that ''whatever court we are in . . . at the end of our task some human being is going to be affected. Some human life is going to be changed . . . and we had better use every power of our minds and our hearts and our beings to get those rulings right.''

The second quote demonstrates an admirable sensitivity on Judge Souter's part. But it begs the question of unenumerated rights. Rights not explicitly written in the Constitution are rights that various judges through a body of decisions and appeals have had to find and place there themselves. They have generally found those rights in response to the kind of sensitivity Judge Souter expresses in this second quote.

While we may celebrate the many examples of activist judges getting ''rulings right,'' we ought to be concerned about the process of those decisions in more than an abstract way. We must not forget that judicial activism, the establishment of unenumerated rights, is not a one way street; it is the same process that produced Dred Scott.

Law is about process, due process. In a constitutional society, no one ought to be above the law or the process that the law demands, especially the courts. When judges go beyond the language of the Constitution to develop unenumerated rights, we ought to ask not only whether the process by which these rights are developed is legitimate; we should also ask what is wrong with the constitutional process to establish rights through legislation and constitutional amendment by elected representatives.

It seems to me that it is time for those of us who vote to ask whether this nation still has a commitment to constitutional democracy. Do we want laws to be made by those accountable through election, or are we willing to allow short cuts through the courts when legislators fail us? Before we give an easy yes, let us remember that we may now have a conservative court that will be active in a way we might not like.

RICHARD BERNDT Vienna