How reliable are the Dead Sea Scrolls as a base to compare against the Masoretic text and the LXX?

Question

I often find people comparing other manuscripts (e.g., Masoretic text, LXX) against the Dead Sea Scrolls in order to determine their accuracy. For example, this thread asked how reliable the LXX was in comparison to the Masoretic text in light of the discovery of the Dead Sea Scrolls. This seems to imply that the Dead Sea Scrolls are the exemplar par excellence by which other manuscripts are measured for accuracy.

So, I ask, how can the accuracy of the Dead Sea Scrolls be assessed, and if indeed this is possible, how accurate are those manuscripts in the Dead Sea Scrolls of books found in the Bible (e.g., 1QIsa1 of the Book of Isaiah)?

Answer 1

The Dead Sea Scrolls are the only ancient Hebrew Bible manuscripts that we have. Everything else in Hebrew is from the 11th century or later. Thus it's natural that the Dead Sea Scrolls loom large in studying the textual history of the Hebrew Bible. However, the Dead Sea Scroll texts don't always agree with each other, and their age is no guarantee of accuracy. By comparing different textual traditions (LXX, but also translations into other languages, the Samaritan Torah, etc.) it is sometimes possible to trace back the history of the text past the era of the Dead Sea scrolls and to identify errors in the Dead Sea scrolls.

Basically, the Dead Sea scrolls are uniquely valuable information to textual critics, but nonetheless other texts also give important information which much be synthesized using the usual tools of textual criticism.