ABSTRACT
At the 1967 meeting at Bellagio the idea of a hierarchy frequently entered the discussions. This was to be expected. If one thinks at all about biological systems, it is natural to simplify the problem of getting a comprehensible picture of what is going on in them, by drawing boundaries around blocks of activities which have a fairly obvious coherence and autonomy; and having one such block exercise control over others, while being controlled by yet another or others. When we have done this, we have already imposed the concept of a hierarchy. Sometimes it is clear that the imposition of hierarchical structure is natural, because the 'blocks' are very apparent in their action. Other times it is extremely hard to find them at all, yet the hierarchical idea has such a grip on us that we still find biological systems of this second kind being thought of in terms of these blocks. This latter situation is particularly common in theories of brain physiology.
