Pulse
06 Apr 2026
One of the most contentious approaches to ethical reasoning is the slippery slope argument (SSA). While many ethicists credit the SSA as having some value, they are at the same time quite wary of it.
Briefly, the SSA warns that permitting a certain policy would incrementally result in morally undesirable and even disastrous consequences. For example, legalising physician-assisted dying (suicide) for patients with terminal illnesses may pave the way for the inclusion of non-terminal cases.
Some ethicists object to the SSA because it is allegedly often associated with logical fallacies. These ethicists often point out that the SSA are often guilty of committing non sequiturs – they assume that because one event occurs, another will eventually follow, even if there appears to be no causal connection.
While some of these objections are valid, they do not entirely discredit the SSA as a justifiable approach to ethics.
This is because ethics has to do not only with evaluating present actions but also with anticipating future consequences. Furthermore, even a cursory survey of the history of ethics shows that societies have routinely shifted from one moral norm to a more permissive and harmful one.
A recent example of the outworking of the slippery slope is the so-called 14-day rule which has for many decades governed human embryo research – specifically the push to extend it to 28 days.
The origins of the 14-day rule can be traced to the early 1980s when the UK assembled the Committee of Inquiry into Human Fertilisation and Embryology to discuss developments in assisted conception. In 1984, what is now known as the ‘Warnock Report’ was published, recommending the 14-day rule which has since become standard regulation for embryo research.
It was Anne McLaren, a member of the committee, who introduced the 14-day limit for embryo research. According to McLaren, confining research to the first 14 days seemed reasonable because it precedes the emergence of the ‘primitive streak’, which is the early developmental precursor of the brain and spinal cord.
However, as Giulia Cavaliere has noted, the setting of this limit to research was also because the committee felt that a compromise solution had to be reached to address different views on embryo research. She writes:
Introducing a cut-off date – in this case the 14-day limit – represented an instance of favouring compromise between competing moral views, beliefs and values over questions of rightness and wrongness.
In other words, in the 14-day rule a practical solution was offered to evade tough philosophical and moral questions about the status of the embryo. Cavaliere’s penetrating assessment of how this rule was arrived at merits careful consideration:
Questions regarding whether or not the embryo has moral status, what moral status stands for and entails, and questions regarding the core features of personhood and the beginning of human life were overridden by other considerations. These considerations included the moment from which the embryo should be granted legal protection, what kind of society can be praised and in what kind of society people can live with a clear conscience. The decision to shift the focus from ontological questions concerning rightness and wrongness to more practical questions is linked to a conception of morality whose role is to address moral matters arising in the context of public policy.
When moral or ethical questions and principles are brushed aside, or when they are narrowed down to the confines of the law and public policy, the risk of the slippery slope presents itself.
Recently, researchers have been urging policy makers to revisit the 14-day rule because research on the embryo beyond 14 days which has been hitherto untenable is now technically possible. Researchers have presented various reasons why current policies and regulations must be changed to allow scientists to work on older embryos.
In their paper recommending that the 14-day timeframe be extended to a 28-day timeframe, John Appleby and Annelien Bredenoord offer several reasons why this change makes sense now.
The period between the 14th and 28th day of the development of the embryo, they point out, is sometimes described as the ‘black box’ of human development. ‘Extending the window for embryo research to 28 days,’ they argue, would allow scientists to study the developmental processes during gastrulation when the first primitive tissues form.’
Furthermore, ‘an extended research window could further improve the safety and success rate of current IVF procedures,’ they argue. It could help scientists better understand birth defects and predict the success of the IVF procedure.
Beyond this, Appleby and Bredenoord argue that extending the window could help scientists in their research on stem-cell derived gametes and gene editing. It could also bolster ground-breaking research on stem cells that would enable scientists to create ‘synthetic’ embryos and organoids.
Based on these considerations, Appleby and Bredenoord made this recommendation at the end of their article:
In order for embryo research to fulfil its potential benefit to humans both now and in the future, we therefore propose that the current limit on research should be extended to 28 days or the equivalent developmental stage that is normally attributed to a 28-day-old embryo.
Their entire argument is premised on two sets of logic, both equally naïve. The first says that once a practice is technically feasible, the current rules or laws must be changed to allow it. The second argues that if something is beneficial or even potentially beneficial, it should be allowed.
Their unprincipled and morally-vacuous pragmatism is clearly evident in this short paragraph:
Although the 14-day rule is viewed by many as a success, it must be ‘fit for purpose’ to remain effective and relevant; it should not become a dogma in itself. Science is changing and regulations need to adapt.
This is not ethics. The entire argument of Appleby and Bredenoord is premised on the dangerous idea that what can be done should be done – a technological imperative fuelled by the tyranny of expedience.
This way of thinking is certainly antithetical to Christian ethics which always asks ontological and moral questions when it comes to embryo research. A case in point is the way in which the National Council of Churches in Singapore (NCCS) has responded to the issue.
In November 2001, the NCCS was invited by the Bioethics Advisory Committee of Singapore (BAC) to participate in a consultation on embryonic stem cell research. The Council accepted the invitation and participated in the consultation by submitting a written response to the BAC’s paper and taking part in closed-door discussions on the topic.
In its response, the NCCS states that it opposes embryonic stem cell research because it results in the destruction of human embryos. The Council explains that according to the Bible, human beings are created in the image and likeness of God (Genesis 1:26-27). The human embryo is a bearer of that image from its conception and therefore should be accorded proper dignity and protection.
The Council therefore could not endorse the so-called 14-day rule. Its objection is not based on public sentiment or the limits of technology, but on a theological anthropology that is grounded in Scripture and that can be defended philosophically.
The danger of the slippery slope is real and those who base their ethical views on superficial pragmatic considerations, a simplistic cost-and-benefit calculus, and scientific and technological advancement are especially vulnerable to it.
Dr Roland Chia is Chew Hock Hin Professor at Trinity Theological College (Singapore) and Theological and Research Advisor of the Ethos Institute for Public Christianity.