According to Feyerabend, scientific progress often does not occur via one theory, T2, making improvements or modifications to another theory, T1, in such a way that all of the material from T1 can be explanatorily reduced to T2 material. This model of scientific progress that Feyerabend is arguing against is known model of progress via intertheoretic reduction. The reason scientific progress often does not occur via intertheoretic reduction is that were progress to occur via intertheoretic reduction, new theories would need to say nothing that was incompatible with old theories—in essence, new theories could only be expansions of or additions to old theories. However, says Feyerabend, oftentimes, new theories completely replace old theories, since some central component of the old theory was false and, hence, could not be preserved.
Even though scientific progress often occurs via replacement of old theories with new theories, do you think that before replacing an old theory with a new theory, scientists ought to attempt to come up w/ a new theory that preserves the elements of the old theory? That is, is there any value to attempting to preserve the elements of an old theory such that scientists should at least try to save those elements before moving on to replace an old theory with a new theory?