Some years ago the "rst author (Y.S.) received an e-mail message from a graduate student in Germany that there was in Europe a group of scientists who do not believe in the existence of follower forces. Later a letter from Denmark noti"ed us about Koiter's article entitled &&Unrealistic follower forces'' [1].
It was interesting for us to know that the elimination of follower forces proposed by Koiter, on the advice of Isaac Elishako!, took place about half a century after Beck's column, a cantilevered column subjected to a follower force, was born in 1952. Since Professor W. T. Koiter was one of the top-most scientists in the "eld of applied mechanics and Professor Isaac Elishako! is one of the most active scientists, the storm of their criticism that follower forces are unrealistic, and that the papers on the e!ect of follower forces should not be accepted for publication, has had far-reaching consequences in the society of applied mechanics. The magnitude of the storm, and to what extent the storm was bitter to scientists who were interested in the concept of follower forces, can be understood easily from Bolotin's confession [2]: &&I met many people arguing about this subject.'' &&The arguments resulted in a temporary personal break of the friendship.'' &&I am not at all a partisan of follower forces. It seems that since 1961 when I had published my book, I never returned to the topic.'' However, in our opinion, their criticism is only partly correct, in the sense that many purely would-be academic/theoretical papers on the e!ect of follower forces not relevant to science and engineering have been published. But it is partly wrong, in the sense that the concept of follower forces is important in order to understand some types of dynamic instability of structures subjected to follower non-conservative loadings, while Koiter said that follower forces are unrealistic in general. It is true that there have been published a vast body of papers dealing with the concept of so-called follower forces which are nothing but purely mathematical exercises having no relevance with physical reality. In such papers, even though follower forces do exist, the mathematical models accommodated with the follower forces*modi"ed versions of Beck's columns*are unrealistic or have no physical reality. Some of them are unduly simpli"ed [3], and some are arti"cially complicated. It is noticed that these unrealistic models are prone to yield, eventually, a new, paradoxical or