{ 1 } - The former practice seeks to achieve a good end by a means which is not intrinsically contrary to human nature, while the latter seeks to achieve a good end by a means which is intrinsically contrary to human nature.
{ 2 } - The language of the former is not self-contradictory, while the language of the latter is, since the language of sexual intercourse is total self-giving, but contraception restricts this self-giving.
{ 3 } - In the former case fertile acts are not deliberately rendered infertile, while in the latter case this is what is intended.
{ 4 } - The former practice involves accepting dialogue, reciprocal respect, shared responsibility, and self-control, and the latter does not.
{ 5 } - The former practice does not avoid having children while the latter does.

Use of the infertile period is just as effective as contraception in avoiding the procreation of children, and must be done for a good reason to be ethical.