"While rejecting atheism, root and branch, the Church sincerely professes that all men, believers and unbelievers alike, ought to work for the rightful betterment of this world in which all alike live; such an ideal cannot be realized, however, apart from sincere and prudent dialogue. Hence the Church protests against the distinction which some state authorities make between believers and unbelievers, with prejudice to the fundamental rights of the human person. The Church calls for the active liberty of believers to build up in this world God's temple too. She courteously invites atheists to examine the Gospel of Christ with an open mind." (Gaudium et spes, 21).

Why would the Fathers have to make the prepositional statement that they made?  Why do they feel "the need" to remind readers that they are not embracing any aspects of atheism?  Has any previous ecuмenical Council ever made such a statement???