The first one is meant to be pro-CL. It says that there are problems that are so difficult or large that they can only be solved with some of the unique features Lisp, such as macros. Of course, all programming languages in use are Turing-complete, so technically you could use any language. In practice, however, the mental capacities of the programmers form a barrier: imagine writing an OS in Brainfuck. So when people are working on such problems in C or Fortran, sooner or later they will - unknowingly - come up with the ad hoc implementation of CL in their program, to get some of that additional abstraction Lisp provides.