42 The very external conditions in which the Church finds itself give added impetus to this striving for religious and moral perfection, for the Church cannot remain indifferent to or unaffected by the changes which take place in the world around. They influence, modify, and condition its course of action in all sorts of ways. As we know, the Church does not exist in isolation from the world. It lives in the world, and its members are consequently influenced and guided by the world. They imbibe its culture, are subject to its laws and adopt its customs. This intimate contact with the world is continually creating problems for the Church and at the present time these problems are extremely acute. The Christian life, as encouraged and preserved by the Church, must resist every possible source of deception, contamination, or restriction of its freedom. It must guard against these things as it would guard against contamination by error or evil. Yet at the same time it must not only adapt itself to the forms of thought and living which a temporal environment induces, one might almost say imposes, on it-provided, of course, such forms are not incompatible with the basic principles of its religious and moral teaching-but it must also strive to approach these forms and to correct, ennoble, encourage, and sanctify them. And this demands of the Church a continual process of self-examination and re-appraisal of its external conduct. This in fact is what the present era is demanding of the Church with such insistence and earnestness.
Source: Ecclesiam Suam (Vatican.va)