Since it was the only Christian Church for the first 1,000 years after Jesus Christ founded it, yes, it obviously is. Jesus founded just one Church, said it was to remain one, and promised that one Church "The Holy Spirit will guide you into all truth", and "Whatsoever you bind upon Earth is bound in heaven", and "He who hears you hears Me". Either He lied, or didn't know what He was talking about, or that one Church still teaches the fullness of truth in unity today. Unity is essential because truth cannot conflict with truth, which means a manmade system of thousands of unauthorized manmade denominations, the teaching of each one conflicting with the teaching of the others, necessarily means widespread untruth. The Catholic Church alone remains one in belief, one in teaching, one in worship, one in biblical understanding throughout the world after 2,000 years, just as its founder intended. the clearly stated will of Jesus Christ concerning His followers was and still is "That they all may be ONE, even as I and My heavenly Father are ONE".