The idea of the air and space environments being part of the same "seamless continuum" pervades Air Force thinking about the nature of space operations. According to doctrine the "aerospace medium" is an indivisible whole where the military activities of the U.S. can perform in this environment are essentially the same whether or not the platform is based in air or in space. Airpower theorist Alexander de Seversky, as quoted in Air Force doctrine, said "The air ocean and its endless outer space extension are one and the same." According to the Air Force's most fundamental expressions of doctrinal thought, Air Force Doctrine Document 1 (AFDD 1) Basic Aerospace Doctrine of the United States Air Force and AFDD 2 (Organization and Employment of Aerospace Forces), the characteristic advantages of operations in the air are identical to the advantages of operations in space. The logical extension of Air Force doctrine implies the lessons learned from a century of airpower experience are directly applicable to operations in space, without modification. A new, and vastly improved, version of Space Operations Doctrine (AFDD 2-2) was published on 27 Nov 01. Written almost entirely by space operations experts, this document opens the door for innovative consideration of the potentially unique contributions from operations in space. However, this otherwise forward-thinking document still begins Chapter One with the assertion "There is no division ... between air and space. Air and space are an indivisible field of operations."