Take, for example, the idea of a grand combination of human energies mustered together in secret, and operating through invisible agencies for the downfall of Christianity,—­an idea which was conveyed to De Quincey in his childhood through the Abbe Baruel’s book exposing such a general conspiracy was existing throughout Europe:  this was the sort of mystery which arrested and engrossed his thoughts.  Similar elements invested all secret societies with an awful grandeur in his conception.  So, too, the complicated operations of great cities such as London, which he call the “Nation of London,” where even Nature is mimicked, both in her strict regularity of results, and in the seeming unconsciousness of all her outward phases, hiding all meaning under the enigmas that defy solution.  In order to this effect it was absolutely necessary that there should be not simply one mystery standing alone by itself, and striking in its portentous significance; there must have been more than this,—­namely, a network of occult influences, a vast organization, wheeling in and out upon itself, gyrating in mystic cycles and epicycles, repeating over and again its dark omens, and displaying its insignia in a never-ending variety of shapes.  To him intricacy the most perplexing was also the most inviting.  It was this which lent an overwhelming interest to certain problems of history that presented the most labyrinthian mazes to be disinvolved:  for the demon that was in him sought after hieroglyphics that by all others had been pronounced undecipherable; and not unfrequently it was to his eye that for the first time there seemed to be an unknown element that must be supplied.  Such a problem was presented by the religious sect among the Hebrews entitled the Essenes.  Admitting the character and functions of this sect to have been those generally ascribed to it no special importance.  But the idea once having occurred to De Quincey that the general assumption was the farthest removed from the truth,—­than there was an unknown x in the problem, which could be satisfied by no such meagre hypothesis,—­that, to meet the urgent demands of the case, there must be substituted for this Jewish sect an organization of no less importance than the Christian Church itself,—­that this organization, thus suddenly brought to light, was one, moreover, that, from the most imperative necessity, veiled itself from all eyes, uttering its sublime articles of faith, and even its very name, to itself only in secret recesses of silence:—­from the moment that all this was revealed to De Quincey, there was thenceforth no limit to his profound interest.  Two separate essays he wrote on this subject,[A] of which he seemed never to tire.