On Mar 14, 10:31 am, WM <mueck...@rz.fh-augsburg.de> wrote: > On 14 Mrz., 08:39, William Hughes <wpihug...@gmail.com> wrote: > > > > > > > > > > > On Mar 13, 11:05 pm, WM <mueck...@rz.fh-augsburg.de> wrote: > > > > On 13 Mrz., 22:41, William Hughes <wpihug...@gmail.com> wrote: > > > > > Let J be a set of the lines of L with no > > > > findable last line. At least two lines > > > > belong to J. Are any lines of J necessary? > > > > Remove all lines. > > > Can any numbers remain in the list? No. > > > Therefore at least one line must remain in the list. > > > > We do not know which it is, but it is more than no line. > > > In other words, it is necessary, that one line remains. > > > However, it is not necessary that any one particular > > line remain. So while it is necessary that the set > > J contain one line, there is no particular line l that is > > necessary. > > Correct. But I have not claimed that there are particular lines.
Then it is a mistake to call particular line necessary e.g. to say "There is a necessary line".