Conjoined Twins, Part II

Dear M:

Thanks for sharing with me your fascinating views on this matter.

I found this point of yours most important:

“we don’t call a person with three feet two people sharing a common foot, so a person with two heads is a single individual with split coexisting personalities.”

But, each head can have a different preference, a different will. Feet can’t do that. So, I think of conjoined twins as two people, not one, just as I think of the mother and the fetus as not one but two different people.

You’ve seen this?

Dyke, Jeremiah and Walter E. Block. 2011. “Explorations in Property Rights: Conjoined Twins.” Libertarian Papers, Vol. 3, Art. 38;

Best regards,


From: M
Sent: Tuesday, February 26, 2019 8:21 AM
To: wblock <[email protected]>
Subject: Conjoined twins


Just some off-the-cuff observations on conjoined twins…

If I understand, the reason conjoined twins are so attached, besides the obvious abnormal prenatal development, is that according to one or more physicians on their case, the “viability” of life after separation is considered very low for one or both, depending on how many organs are shared. 

So, if one or both personalities sharing the same body cannot survive apart, you could look at it like an ongoing viability issue from the 20th week. In other words, one or both will die apart. 

In fact, I do not know the cases of how many conjoined twins demand separation, but I imagine this procedure is very high risk for both, even if one or both live through the procedure.

One of the problems or errors of libertarian thought here, is assuming two individuals exist with their own separate individual rights. In fact, this also points to a fallacy in the abortion debate… that a fetus is sufficiently distinct from the mother such that it can be expected to live, or has the right to live, BEFORE it has “viability” sufficient to live outside the womb if medically extracted. 

So, in cases of involuntary pregnancy such as rape, the mother has the right not to care for the fetus before it is viable, including continuing to provide a natural incubator, and has the right to evacuate the fetus if it is viable so that it no longer makes demands of her body for care.

In the case of conjoined twins, we must treat this medical abnormality as a single individual. Just as a normal human with one head can be of two minds on an issue, a conjoined twin set is a single individual with two minds on an issue. That is, in every way the personalities share common organs and the same body, the literally split personality is still a single individual.

Therefore, it has individual, not group identity. According to it’s own biology, it must find a way for the split personalities to cooperate such that its individual existence continues.

Put another way, we don’t call a person with three feet two people sharing a common foot, so a person with two heads is a single individual with split coexisting personalities.

All my best,



1:47 am on June 25, 2019

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