18 When this greatest fundamental truth has been overturned or weakened, it follows that those truths, also, which are known by the teaching of nature must begin to fall - namely, that all things were made by the free will of God the Creator; that the world is governed by Providence; that souls do not die; that to this life of men upon the earth there will succeed another and an everlasting life.
Source: Humanum Genus (Vatican.va)