I believe the word “infidel” is not particular to any religion. I believe we are all created in the image of God, in fact, we are all God, or at one with God, at our deepest core essence. I think “infidel” refers to one who does not believe that God is none other than the Self. The “infidel” is the individual personality who identifies with the body and thoughts and not the Divine Indweller. Therefore we are all “infidels” save the sacred few who have transcended the notion of the limited self. The ancient mystics of all tradtitions have said this.
