7 Now, it cannot be difficult to find out which is the true religion, if only it be sought with an earnest and unbiased mind; for proofs are abundant and striking. We have, for example, the fulfilment of prophecies, miracles in great numbers, the rapid spread of the faith in the midst of enemies and in face of overwhelming obstacles, the witness of the martyrs, and the like. From all these it is evident that the only true religion is the one established by Jesus Christ Himself, and which He committed to His Church to protect and to propagate.
Source: Immortale Dei (Vatican.va)