8.2 Protagonists in the Shadows: Thomas Hayes and Alan S. Parkes

Summary: Chapter VIII (II)

Protagonists in the shadows (II): Thomas Hayes and Alan S. Parkes


I. Hayes and the “reproductive act”

Thomas Hayes introduced the novel concept of the “reproductive act,” opposing it to the singular sexual act. The author intended in this way to discredit the moral doctrine about sexuality based on natural law professed by the Church.

This view was confirmed by Frank Maurovich on the 45th anniversary of the encyclical Humanae Vitae. In 1964, Maurovich, editor of a Catholic journal, was visited by biophysicist Thomas Hayes of the University of California. At the time, Hayes told Maurovich that he had the solution to the problem of birth control in the Church. Maurovich urged Hayes to present his ideas in an article, which eventually appeared as “The Biology of the Reproductive Act” in the journal Cross Currents in 1965. Maurovich then sent the article to Belgian Cardinal Leo Joseph Suenens, who in turn delivered it to the Executive Committee of the Papal Commission for the Study of Birth, Population and the Family (PC).

Hayes’s article went practically unnoticed both among the general public and among the cultivators of the biological sciences or moral theology. A thorough search on the Internet confirms this. But it had a significant impact on the conclusions of the PC.

Hayes’ thesis

Hayes’ article develops the concept of “reproductive act” as a biological and moral unit to judge the various methods of birth control. The proposed new concept replaces the act of sexual intercourse. Hayes implies that the reproductive act comprises the set of component acts (male, female, co-sexual) that are required for fertilization to take place. Given the periodicity with which the ovary releases the oocytes, the reproductive act usually takes a month to complete. Thus understood, this act may include a more or less elevated number of acts of sexual intercourse, each and every one of them being subordinated to the corresponding reproductive act during which they occur.

Hayes argues that, according to his concepts of reproductive act and sexual act, the method of rhythm is not different from other methods of birth control (diaphragm, coitus interruptus, condom, anovulatory pill) and therefore should not be taken as a natural method of birth control.

Hayes and the Papal Commission

The ideas of Hayes, coming with the alleged “seal of approval” of scientific knowledge, came to the Commission of Cardinals and Bishops and, finally, to the Pope. In the final report that Riedmatten delivered to the Pope, Hayes’s thesis is used as a starting point for two proposals of great importance: first, that of depriving the singular conjugal acts of substantive ethical meaning, since they are subsumed in the month-long and inclusive reproductive act; and second, to declare that there is no moral distinction between natural methods of birth control and artificial methods, whether mechanical or chemical. Both proposals clashed head-on with the doctrine hitherto proclaimed by the Magisterium of the Church.

Hayes after the Humanae Vitae

The detractors of the encyclical assign to the Pope the idea that every conjugal act must be de facto open to fertilization, which, in their view, is only carried out in the “reproductive act” defined by Hayes. In reality, what affirms Paul VI’s view is that the use of marriage must on each occasion be open to procreation. The critics of the encyclical turn the Pope’s moral requirement into a physiological requirement, to which the encyclical does not even allude.

Humanae Vitae has been accused both of ignoring the biology of human sexuality as well as overidentifying itself with it, thus basing its doctrine on a naturalistic and biologistic interpretation of natural law. But the supposed physiologism of the encyclical cannot compete in content or intensity with the Hayes theory that elevates his notion of reproductive act to the level of the ruling metric in the determination of the ethical norm of the conjugal relation.


II. Alan Parkes and the simile of the chicken egg


Sir Alan S. Parkes (1900-1990) devoted considerable attention to the control of fertility in the human species. He was a great promoter of contraception and actively participated in the population programs of the International Planned Parenthood Federation, the Royal Commission on Population Control and served on the Advisory Committee of the World Health Organization.

The simile of the Chicken Egg

Parkes sought to discredit the pro-life activists’ claim that some contraceptives could act through an abortifacient effect. For this, he defended the idea that conception and implantation are equivalent expressions that designate the same phenomenon. He quickly became one of the idea’s most energetic and effective propagators.

Parkes recognized that contraceptive procedures interfered with fertilization and, frequently, with implantation. But for him that did not mean he could call them abortifacient, since, in the widely-shared ideology of Parkes, conception was a complex and lengthy process in which, as a final phase, implantation was part. In defense of this thesis, Parkes adduced his analogy of the hen’s egg, a simile he used repeatedly in his articles during lectures during the 1960s.

“There is no universally accepted definition of the term conception, but it must refer, in my opinion as a biologist, not to fertilization but to the implantation of the fertilized egg in the uterus. For example, it is not said that a chicken conceives when its egg is fertilized, or that it aborts when it is laid. This is a very important point because we are now working a lot on the control of the implantation” (June 20, 1961). In 1964 Parkes published in the journal Nature a summary of a discourse in which the simile of the chicken egg is constituted as the cornerstone of the ethical legitimation of implantation as the temporal limit of contraception.

Is the simile of Parkes sustainable?

Parkes did not offer evidence based on biology in favor of his claim. But an argument by authority is not per se valid. Nor is it a pedagogical resource that clarifies the problem. In fact, the comparison of Parkes does not seem legitimate from a scientific perspective, since it ignores the basic difference that exists between the internal gestation of mammals and the oviparity of birds.

The simile of the chicken egg had a short life. After 1965, Parkes stopped using it. It is likely that he noticed the profound logical and scientific weakness of his analogy – it was witty, but unfounded. However, he continued insisting on the identity of conception and implantation, and tenaciously maintained that inhibiting implantation does not present ethical problems for the practice of contraception.



Author: Gonzalo Herranz, University of Navarra.  Email: gherranz@unav.es


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