WHILE MRS. DOUGLAS WAS SPEAKING too freely on a subject she knew too little about, Jubal E.  Harshaw, LL.B., M.D., Sc.D., bon vivant, gourmet, sybarite, popular author extraordinaire, and neo-pessimist philosopher, was sitting by his swimming pool at his home in the Poconos, scratching the thick grey thatch on his chest, and watching his three secretaries splash in the pool.  They were all three amazingly beautiful; they were also amazingly good secretaries.  In Harshaw's opinion the principle of least action required that utility and beauty be combined.