Below are key passages giving reasons for Canadian Conference of Bishops dissent on contraception:
17. It is a fact that a certain number of Catholics, although admittedly subject to the teaching of the encyclical, find it either extremely difficult or even impossible to make their own all elements of this doctrine. In particular, the argumentation and rational foundation of the encyclical, which are only briefly indicated, have failed in some cases to win the assent of men of science,or indeed of some men of culture and education who share in the contemporary empirical and scientific mode of thought. We must appreciate the difficulty experienced by contemporary man in understanding and appropriating some of the points of this encyclical, and we must make every effort to learn from the insights of Catholic scientists and intellectuals, who are of undoubted loyalty to Christian truth, to the Church and to the authority of the Holy See. Since they are not denying any point of divine and Catholic faith nor rejecting the teaching authority of the Church, these Catholics should not be considered or consider themselves, shut off from the body of the faithful. But they should remember that their good faith will be dependent on a sincere self-examination to determine the true motives and grounds for such suspension of assent and on continued effort to understand and deepen their knowledge of the teaching of the Church.
Preliminary Pastoral Guidance
26. Counsellors may meet others who, accepting the teaching of the Holy Father, find that because of particular circumstances they are involved in what seems to them a clear conflict of duties, e.g., the reconciling of conjugal love and responsible parenthood with the education of children already born or with the health of the mother. In accord with the accepted principles of moral theology, if these persons have tried sincerely but without success to pursue a line of conduct in keeping with the given directives, they may be safely assured that, whoever honestly chooses that course which seems right to him does so in good conscience.
27. Good pastoral practice for other and perhaps more difficult cases will be developed in continuing communication among bishops, priests and laity, and in particular in the document we have promised to prepare. In the meantime we earnestly solicit the help of medical scientists and biologists in their research into human fertility. While it would be an illusion to hope for the solution of all human problems through scientific technology, such research can bring effective help to the alleviation and solution of problems of conscience in this area.