“Our fight is not against human foes but against cosmic powers, against the authorities and potentates of this dark world, against the superhuman forces of evil in the heavens.” –Eph. 6: 12.
“The children, the poets, and the philosophers were right; as there is one Face above all worlds merely to see which is irrevocable joy, so at the bottom of all worlds that face is waiting whose sight alone is the misery from which none who beholds it can recover. And though there seemed to be, and indeed were, a thousand roads by which a man could walk through the world, there was not a single one which did not lead sooner or later either to the Beatific or the Miserific Vision”.(C.S.LEWIS, Perelandra)
The prince of darkness, “the ruler of this world”, (Jn 14:30), “the father of lies” (Jn 8:48), “the evil one” (Mt.13:19) is ultimately the enemy behind all our enemies, one whose destructive genius we can in no way underestimate. As a Catholic writer who understood Satan’s power stated:
“Who can measure the reach of his thought, who had been Melkor, mighty among the Ainur of the Great Song, and sat now, a dark lord upon a dark throne in the North, weighing in his malice all the tidings that came to him, and perceiving more of the deeds and purposes of his enemies than even the wisest of them feared” (J.R.R.TOLKIEN, The Silmarillion)
Nevertheless, his influence is limited:
“The Evil One can not act directly on our higher faculties, the intellect and the will. God has kept these as a sanctuary for Himself, and He alone can enter there and touch the mainspring of the will without doing violence to it. The devil, however, can act directly on the body, on our exterior and interior senses, and particularly on the imagination and the memory as well as on the passions which reside in the sensitive appetite. Thus, the devil acts indirectly on the will, soliciting its consent through the various movements of the sensitive appetite. The will, however, as St. Thomas remarks, remains ever free to give or refuse consent.” (Adolphe Tanquerey, The Spiritual Life)
Ultimately “the buck stops here”: at our “yes” or “no” to temptation. Nor is Satan the principal source of many of our temptations which spring from the fall-out of our previous sins and present imprudence of judgment.