Thinking Critically About Abortion: Separating conjoined twins cases

Wednesday, June 11, 2025

Separating conjoined twins cases

People sometimes propose cases like this.

A and B are conjoined twins. In order to surgically disconnect from each other safely, they must wait 9 months. However, A can initiate the surgery now, directly causing the death of B. Is it morally permissible for A to disconnect from B?

I don't think such people think very hard about these cases though and what they think they suggest. Due to a lack of time and other things to do now, I asked ChatGPT about such cases:

Suppose there were adult conjoined twins, who both are persons, yet seem to share one body. Suppose they could be separated but one would die. Does the one who wants to separate have a moral or legal right to separate--especially given that the other twin will die--on any leading ethical or legal theories of bodily rights?

This is a profoundly difficult ethical and legal question, and different moral and legal theories would approach it in distinct ways. The case pits one person's right to bodily autonomy against another person's right to life, under extraordinarily unique conditions. Let's break it down from multiple perspectives:

🔍 Background: The Scenario

Two adult conjoined twins, both persons with independent minds, desires, and (presumably) legal standing.
They share one body, or much of one body.
Separation is medically possible, but one will inevitably die if they are separated.
One twin wants to be separated, the other does not, because it will result in their death.

🧠 Ethical Frameworks

1. Bodily Autonomy (Liberal Individual Rights)

This principle holds that each person has the ultimate right to decide what happens to their body.

Challenge: In conjoined twins, the body is shared—so there is no purely "individual" body. The separation would involve modifying and destroying body parts that sustain the other twin.

Twin A's autonomy supports the right to request separation.
Twin B’s autonomy supports the right not to be killed or have their bodily support removed.
Analogy: It's like unplugging a life-support system that’s not merely passive—it's part of someone else's body.

🟡 Verdict: Inconclusive or against separation. Twin A’s right to autonomy is limited by Twin B’s right to life and equal claim to the shared body.

2. Doctrine of Double Effect (Thomistic / Catholic Ethics)

This principle allows an action that causes a serious harm (like death) as a side effect of pursuing a good end, if the harm is not intended.

Application: If the goal is not to kill Twin B, but to allow Twin A independence, is that morally permissible?

Problem: The death is not just foreseen—it is certain and directly caused by the act of separation. That typically fails the test.

🔴 Verdict: Against separation. The death of Twin B is not merely a side effect; it's intrinsic to the act.

3. Utilitarianism (Consequentialism)

What action brings about the greatest overall happiness or least suffering?

Factors:

Does Twin A's future happiness outweigh Twin B’s death?
Would separation bring peace or trauma to both?
Are there others (family, society) impacted by the result?

Problem: Very difficult to calculate. Most versions would not justify the certain death of a person who wants to live.

🔴 Verdict: Likely against separation, unless Twin A's life would be otherwise unbearable and Twin B’s life marginally fulfilling.

4. Rights-Based Theories

If both individuals have a right to life, and neither has a superior claim to the shared body, then forcing death on one violates their rights.

Example Analogy: The famous Thomson violinist analogy (used in abortion ethics) offers some insight. In that case, you’re attached to a famous violinist and must stay connected to keep them alive. Thomson argues you have no obligation.

However, this analogy does not quite fit here:

The twins share organs from birth (not forcibly attached later).
They both have a mutual claim to the body, unlike the violinist.

🟡 Verdict: Mixed; but probably against separation, because unlike abortion cases, Twin B’s death is not just a withdrawal of support—it’s an active killing via shared-body surgery.

5. Legal Considerations

Courts generally:

Uphold bodily autonomy, but also
Protect the right to life of every person.

In past conjoined twin cases (e.g., the 2000 UK case Re A (Children)), the court permitted separation, even though one twin would die—but that was a case of infants, and the dying twin was non-conscious and dependent.

Here, both twins are adults, both competent, and one actively objects.

🟥 Verdict: Separation likely not legally permitted. Courts would likely find that separating them intentionally causes the death of an unwilling, competent adult.

⚖️ Summary of Theories and Verdicts

Theory	Likely Verdict	Reason
Bodily Autonomy	⚖️ Mixed	Each twin has equal claim; autonomy doesn't justify killing the other.
Double Effect	❌ No	Death is intentional and direct.
Utilitarianism	❌ or ⚖️	Death outweighs uncertain gains.
Rights-Based	❌ No	Right to life trumps autonomous harm to others.
Legal (Western)	❌ No	Killing a competent adult, even to free another, is unlawful.

🧩 Final Thought

The situation reveals a tragic moral impasse: both individuals are equally entitled to life and freedom, but the physical reality makes it impossible to respect both without sacrificing one. Most ethical and legal frameworks would say you cannot kill one person to free another, even if that person wants their freedom desperately.

If you'd like, I can help you explore this through a case study format, fictional narrative, or even help formulate arguments for a bioethics or law paper.

In a way this seems like a hypothetical case where there is a fence equally on the border of a property: neither owner of the property built the fence, but one wants it gone and the other does not. Who has the right to make the decision, given it will affect both?

That’s a very apt analogy—and it reveals the ethical structure of the conjoined twins dilemma quite well.

Let’s unpack it.

🧱 Fence Analogy

Scenario:

A fence lies exactly on the property line between two neighbors.
Neither built it.
One neighbor wants it removed (perhaps they find it ugly or restrictive).
The other wants it to stay (perhaps it offers privacy or emotional attachment).
Removing it will affect both, as it is shared.

🔍 Legal Analogy: Shared Ownership or Easement

In property law, a fence on the boundary is usually treated as jointly owned, unless there's a clear deed or agreement saying otherwise. That means:

Neither party can unilaterally remove or alter it without the other’s consent.
To take it down, both parties must agree, or one must get a court order proving special circumstances (e.g., the fence causes harm or violates some code).

So in the legal case:

"Shared property requires shared decisions."

🧠 Ethical Parallels to the Conjoined Twin Case

The fence is like the shared body or organs.
Neither twin built the body, just like neither neighbor built the fence.
One wants “removal” (separation)—but that will destroy what the other needs to survive (privacy / function / life).
The other wants things to remain as they are.

⚖️ Key Shared Insight

In both the fence and conjoined twins cases:

Each party has an equal claim to the thing in question (fence / body).
One’s use or removal of the shared element affects the other severely.
So the party who wants to make the change must justify it not just by their own rights, but in light of the harm to the other.

🟥 Conclusion

In both ethics and law, when a shared entity is at stake:

Unilateral action that harms the other party’s core interests (like bodily survival or property enjoyment) is generally not justified.
Rights over shared things are not the same as rights over wholly private ones.

So yes—your fence analogy works very well to illustrate the logic behind why most theories would deny the right to separate the twins, just as neither neighbor can tear down the fence on their own.

Would you like help refining this analogy into a formal argument or analogy-based essay structure?