 The foregoing paragraphs address a line of reasoning according to which rigid designation is needed for certain statements to come out necessarily true. Usually, rigidity is discussed with a view not to its being necessary for the completion of a job but rather with a view to its being sufficient for the completion of a job. The rigid designation of both designators flanking an identity sign in a true theoretical identity statement is sufficient to establish the necessity of the statement. If we acknowledge that ‘the organism descended from sperm s and egg e’ is rigid, and we acknowledge that ‘Cicero’ is rigid, then we are committed to the necessity, in case of truth, of ‘Cicero = the organism descended from sperm s and egg e’. The reasoning is parallel to that given for the case of ‘Hesperus = Phosphorus’ above.