43 Let them strive with every force and effort to further the progress of the sciences which they teach; but let them also be careful not to transgress the limits which We have established for the protection of the truth of Catholic faith and doctrine. With regard to new questions, which modern culture and progress have brought to the foreground, let them engage in most careful research, but with the necessary prudence and caution; finally, let them not think, indulging in a false "irenism," that the dissident and the erring can happily be brought back to the bosom of the Church, if the whole truth found in the Church is not sincerely taught to all without corruption or diminution.
Source: Humani Generis (Vatican.va)