What is ‘Natural Law’?

Over the past 50 years varying theories on Natural Law have proliferated. We hope to do justice to them through our online readings and our extensive bibliography. But we do not intend to enter deeply into the many intricate and complex theoretical issues linked to Natural Law theory. We have a more pragmatic aim in view.
We wish to focus on the interpretation of Natural Law that currently underlies official Catholic teaching on sexuality.
The main question we want to address on these pages can be summed up as follows: Should human reason [= conscience] not play 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?
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.

1. The physical interpretation
The centre of gravity of Natural Law lies in physical nature.
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).
Implications
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.
Sources
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
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2. The rational interpretation
The centre of gravity of Natural Law lies in human intelligence.
Dr Columba Ryan OP, “Saint Thomas and the Natural Law”, THE TABLET 27 March 1965, pages 22-23.
Implications
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.
Sources
The rational interpretation of Natural Law goes back to the theology of Saint Thomas Aquinas. However it has been re-formulated by modern theologians.
