St. Mark says: “Be Catholic!” Where does he say that? Mark, 9:40 is not as simple as it seems to be: “Anyone who is not against us is for us.”
Catholics are blessed to understand the meaning of “us”. The “us” to whom Jesus referred must be to Himself and His Disciples.
We know that Jesus Ordained the Disciples as The First Catholic Bishops. We know they were Catholic Bishops because they founded Catholic Churches. Those Catholic Churches between India and Spain sent Catholic Representatives to Catholic Councils. Those Councils were called by Catholic Successors to Peter for hundreds and hundreds of years.
There is no doubt about that.
So, we know that St. Mark says: “Be Catholic!” when he quotes Jesus: “Anyone who is not against us is for us.” It is clear that “us” clearly refers to The Catholic Church.
Since The Only Church Jesus Founded has not changed a single Doctrine in The Faith Handed Down From The Apostles, and it is clear that “Jesus Christ is the same yesterday, today, and forever.”, we may see that the “us” in:
“Anyone who is not against us is for us.” refers to The Church He Founded. We find a deeper understanding by reading “Anyone who is not against The Catholic Church is for The Catholic Church.”
It is difficult to ignore the specific nature of “us” makes any other interpretation unreasonable.
That is why we see so clearly that St. Mark says: “Be Catholic!”
Those whose vanity has not led them to disbelieve and disrespect The Decree By Which Jesus Brought The Only Church He Founded Into Being:
“Verily, verily I say unto you thou art Peter and on this rock I build My Church and the gates of hell shall not prevail against it. I give you the keys to The Kingdom of Heaven.” understand that St. Mark says: “Be Catholic!”