Natural Law as the basis for doctrine on birth control

People should know the truth!
In recent encyclicals Popes have published a crucial doctrinal statement:

The use of artificial means of birth control is forbidden in all circumstances because it is in conflict with Natural Law.

We wish to focus on the interpretation of Natural Law that currently underlies such official Catholic teaching on sexuality.

The main question we want to address can be summed up as follows: Should human reason [= conscience] not pay a more substantial role in assessing what is according Natural Law and what is not than is allowed for in the official instructions of the Catholic teaching authority?

We explore this question in detail on a separate website ( but a short explanation may be helpful at this stage.

There are at present two main interpretations of Natural Law. The assumptions underlying these interpretations are often hidden and the argumentation followed rather complex. As a starting point for a meaningful discussion I have therefore decided to present the two interpretations in simplified and stark ‘sketches’. These will clearly show the difference between them and serve as portals for more detailed documentation.

John Wijngaards

The Physical Interpretation

The centre of gravity of Natural Law lies in physical nature.

The source of marriage law?

Summary view: God the Creator has clearly laid down his immutable intention in the way things are made. We can find this intention [= Natural Law] by carefully studying physical nature.

The Rational Interpretation

The centre of gravity of Natural Law lies in human intelligence.

Conscience determines what is right or wrong

Summary view: God has created human beings in his own image so that they can creatively shape their world. By their intelligence they can discern what is right or wrong [=Natural Law].

Typical assertion: “A couple using artificial contraceptive devices at any time are guilty of serious sin because it interferes with nature . . . The reason why the artificial prevention of births is immoral is written into the very nature of the sexual organs and the marital act itself. The sex organs were made by God to reproduce the human race. Only when husband and wife unite naturally is the union of sperm possible. Therefore the primary purpose of the marital act is the conception of human life.”
Mgr G. A. Kelly, The Catholic Marriage Manual, Random House 1958, pages 47-48 (with a foreword by Francis Cardinal Spellman, Archbishop of New York).
Typical assertion: “Where the reasoning [of conscience] is in fact sound, and the facts truly established, we may say of any conclusion [reached by conscience] that it does belong, at its proper level, to natural law, and that it is therefore the law of God reflected in human understanding.”
Dr Columba Ryan OP, “Saint Thomas and the Natural Law”, THE TABLET 27 March 1965, pages 22-23.


The recent teaching authority of the Catholic Church – under Popes Pius XI, Paul VI, John Paul II and Benedict XVI – has followed the physical interpretation.

As a result official Catholic marriage law forbids the use of contraceptives by married couples, homosexual intimacy, artificial insemination and so on.

Based on a ‘physical’ reading of Natural Law, these prohibitions are prescribed as absolute, valid in all circumstances and unchangible. Transgressions are called intrinsically wrong.


Men and women are called upon to discern what is right and wrong within the complex and changing circumstances of their lives.

For instance, within the overall situation of maintaining a loving relationship between husband and wife and providing a secure upbringing for children, artificial birth control may be discerned to be the right responsible choice.

The same applies to other circumstances, such as a loving relationship between homosexuals and the responsible use of medical advances.


The physical interpretation of Natural Law adhered to by present-day Catholic authorities derives from scholastic philosophy and theology.

Readings on the Physical Interpretation of Natural Law


The rational interpretation of Natural Law goes back to the theology of Saint Thomas Aquinas. However it has been re-formulated by modern theologians.

Readings on the Rational Interpretation of Natural Law