A common trait in all the diverse papers in this double issue of CHK is that they criticize theories by pointing to their 'blind spots.' As you all know the blind spot in the eye is the area where the nerves from the eye go through the retina and up to the brain. We cannot see with that area, but what is worse: we cannot see that we cannot see with that part of the retina. This the main point in the metaphorical use of the concept of blind spot in philosophy of science. Luhmann expresses it by saying that the blind spot for every theory is the first distinction from which observations of a theory are done. We cannot observe and use that difference in our theories at the same time. This is probably also what made Thomas Kuhn claim incommensurability between members of different paradigms. Although we know that our worlds still have overlaps enough to make us able to communicate about all subjects known to man, those blinds spots do make it rather difficult sometimes.