The author is not used to writing on assigned topics and does not intend to deviate from this principle in future, but since he is in various ways indebted to the editors of this special issue, he could not very well turn down their request to contribute to their endeavour. The author has therefore consulted two experts in the field, F. and C., and asked them for their views on the question that makes up the title given. What follows in this article is a précis of their discussion at which the author was present. Since one of them objected to being taped, no recording of the discussion was made. However, both experts have authorized the text confirming that it is a fair rendition of their ideas and concerns.