St. John's description of the "mark of the Beast" is a literary allusion to Deuteronomy 6:8:
4 Hear, O Israel, the Lord our God is one Lord. 5 Thou shalt love the Lord thy God with thy whole heart, and with thy whole soul, and with thy whole strength. 6 And these words which I command thee this day, shall be in thy heart: 7 And thou shalt tell them to thy children, and thou shalt meditate upon them sitting in thy house, and walking on thy journey, sleeping and rising. 8 And thou shalt bind them as a sign on thy hand, and they shall be and shall move between thy eyes [forehead]. 9 And thou shalt write them in the entry, and on the doors of thy house.
Those "marked" by "the Beast" will be those who refuse to acknowledge the true God or His Commandments. They will choose the pleasures of this world over the promise of the world to come. This is a fundamental inversion of the command laid out in Deuteronomy 6. It represents an inversion of reality, one in which man (self) is the highest authority. It is narcissistic humanism as opposed to apostolic Catholicism. And the primary entity pushing the inversion will be the head of the counterfeit "Catholic Church," a illegitimate usurper "Pope" sitting in the Chair of St. Peter.