Leon Kass: revision 1 to 2 — Future Human Wiki

Revision 1

Revision 2

categories: ["people", "society"]

tags: ["bioethics", "bioconservatism", "human dignity", "cloning", "mortality"]

summary: "American physician and bioethicist who chaired the President's Council on Bioethics and made the strongest philosophical case that mortality gives human life its meaning."

summary: "American physician and bioethicist who chaired the President's Council on Bioethics and made the strongest philosophical case that mortality gives human life its meaning."

updated: "2026-07-27"

updated: "2026-10-29"

issues: ["The 2004 removal of two council members is described without a source."]

---

{ "label": "Education", "value": "MD Chicago (1962); PhD Harvard (1967)" },

{ "label": "Known for", "value": "The wisdom of repugnance", "link": "/wiki/bioconservatism" },

{ "label": "Field", "value": "Bioethics; political philosophy" },

{ "label": "Role", "value": "Chair, President's Council on Bioethics, 2001–2005" },

{ "label": "Role", "value": "Chair, President's Council on Bioethics, 2001-2005" },

{ "label": "Affiliation", "value": "University of Chicago; American Enterprise Institute" }

]

}

```

**Leon Kass** is an American physician, biochemist and bioethicist who argues that biotechnology's

**Leon Kass** is an American physician, biochemist and bioethicist. He argues that the central

central danger is not accident or inequity but the erosion of the goods that make a human life

danger of biotechnology is the erosion of the goods that make a human life worth living, rather

worth living — and that mortality, effort and the unchosen character of what is given to us are

than accident or inequity, and he counts mortality, effort and the unchosen character of what

among those goods. He chaired the President's Council on Bioethics from 2001 to 2005 and is the

is given to us among those goods. He chaired the President's Council on Bioethics from 2001 to 2005 and is the

most philosophically substantial exponent of [[bioconservatism]].

## Career

and social policy, taught at St John's College in Annapolis, and joined the University of Chicago's

Committee on Social Thought in 1976, where he taught for more than three decades. He has been a

fellow at the American Enterprise Institute. His books range beyond bioethics into readings of

Genesis and a study of the ethics of eating, and this is not incidental: his method treats the

Genesis and a study of the ethics of eating. The range follows from his method, which builds

meaning of ordinary human activities as the material from which bioethical judgement is built.

bioethical judgement out of the meaning of ordinary human activities.

## Key arguments

Kass's 1971 article in *Science* is the origin point of his position and, arguably, of American

bioethics as a distinct enterprise.[^kass1971] He asked what would follow from technologies then

just visible — in vitro fertilization, prenatal diagnosis, and the eventual prospect of

just visible: in vitro fertilization, prenatal diagnosis, and the eventual prospect of

[[germline-editing|heritable genetic modification]] — and argued that each would be adopted for compelling humanitarian reasons while cumulatively changing

[[germline-editing|heritable genetic modification]]. Each, he argued, would be adopted for

the relations of parent to child and physician to patient. He was writing seven years before the

compelling humanitarian reasons, and together they would change the relations of parent to child

first IVF birth. Several of the specific predictions did not hold; the structural claim, that

and physician to patient. He was writing seven years before the first IVF birth. Several of the

each individual step is defensible and the aggregate is not chosen by anyone, has worn well and

specific predictions did not hold. The structural claim has worn well: each individual step is

recurs throughout debates over [[polygenic-embryo-screening]] and [[designer-babies]].

defensible, and nobody chooses the aggregate. It recurs throughout debates over

[[polygenic-embryo-screening]] and [[designer-babies]].

### The wisdom of repugnance

In a 1997 essay written in response to the cloning of Dolly, Kass argued that visceral revulsion at

certain practices can carry moral knowledge that argument has not yet articulated.[^kass1997]

Repugnance, on this account, is "the emotional expression of deep wisdom, beyond reason's power

fully to articulate it" — a signal that something is being violated even when the violation resists

fully to articulate it", a signal that something is being violated even when the violation resists

formal statement. Applied to [[human-cloning]], the argument holds that the widespread reaction

against it registers real damage to the meanings of parenthood, individuality and generational

succession.

> [!debate] The obvious objection

> Repugnance has historically attached to interracial marriage, homosexuality, dissection and

> vaccination. Critics including Martha Nussbaum, Arthur Caplan and Steven Pinker argue that

> disgust is a poor moral instrument precisely because it is so easily attached to the unfamiliar,

> disgust is a poor moral instrument because it attaches so easily to the unfamiliar, and that

> and that Kass supplies no criterion for distinguishing wise repugnance from prejudice. Kass's

> Kass supplies no criterion for distinguishing wise repugnance from prejudice. Kass replies that

> reply is that repugnance is evidence to be examined rather than a verdict, and that the

> repugnance is evidence to be examined rather than a verdict, and that admitting only what can be

> alternative — admitting only what can be formalized — arbitrarily discards most of moral

> formalized would arbitrarily discard most of moral experience.

> experience.

### Mortality and meaning

constitutive of four goods: interest and engagement, since a finite span makes time matter;

seriousness and aspiration, since the pressure of an ending drives people to attempt things;

beauty and love, which depend on the perishability of what is loved; and virtue, since the highest

form of it involves risking or spending a life that cannot be replaced. Add unlimited time, he

form of it involves risking or spending a life that cannot be replaced. Unlimited time, he argues,

argues, and each good is not increased but dissolved.

would dissolve each of these goods rather than increase it.

The argument is not that longer life is bad but that a life without a horizon would be a different

Kass does not claim that longer life is bad. His claim is that a life without a horizon would be a

and lesser kind of thing, and that a society organized around postponing death indefinitely would

different and lesser kind of thing, and that a society organized around postponing death

sacrifice the succession of generations that renews it. Proponents of life extension answer that

indefinitely would sacrifice the succession of generations that renews it. Proponents of life extension answer that

the goods Kass names attach to the *possibility* of death, which no plausible technology removes;

that no one at seventy in good health regards their own continuation as a loss of seriousness; and

that the argument, taken literally, condemns most of the mortality decline of the past

deliberately composed of people who disagreed, and its reports are unusually discursive for

government documents. *Human Cloning and Human Dignity* (2002) recommended a permanent ban on

reproductive cloning and, by a divided vote, a moratorium on research cloning. *Beyond Therapy*

(2003) examined enhancement directly under four headings — better children, superior performance,

(2003) examined enhancement directly under four headings (better children, superior performance,

ageless bodies and happy souls — and remains one of the few official documents to treat

ageless bodies and happy souls) and remains one of the few official documents to treat

[[human-enhancement]] as a coherent subject rather than a set of unrelated products.[^council2003]

Its treatment of pharmacological mood and memory alteration anticipates arguments now made about

[[moral-enhancement]], and its chapter on performance covers ground that

Bostrom's "In Defense of Posthuman Dignity" is substantially a response to him and to Francis

Fukuyama.

His influence is nonetheless real, in two forms. He supplied the vocabulary in which non-consequentialist

His influence is nonetheless real. He supplied the vocabulary in which non-consequentialist

objections to biotechnology get made, and versions of his arguments now appear from writers who

objections to biotechnology are made, and versions of his arguments now come from writers who share

share none of his politics — in disability-rights criticism of selection, in worries about the

none of his politics: in disability-rights criticism of selection, in worries about the

commodification of reproduction, and in [[disability-rights-and-enhancement|expressivist objections]]

commodification of reproduction, and in

to screening. And he was early in seeing that the important questions would be about enhancement

[[disability-rights-and-enhancement|expressivist objections]] to screening. He also saw early that

rather than about safety, at a time when most bioethics was still organized around consent and risk.

the important questions would concern enhancement rather than safety, at a time when most bioethics

was still organized around consent and risk.

The unresolved point in his work is the boundary. Kass accepts antibiotics, surgery and the

His work leaves the boundary unresolved. Kass accepts antibiotics, surgery and the mortality

mortality decline they produced, and rejects the technologies that would extend the same trend. No

decline they produced, and rejects the technologies that would extend the same trend. No

formulation he has offered specifies where the line falls or why it falls there, and until one

formulation he has offered specifies where the line falls or why it falls there. Until one does,

does, the strongest case against radical life extension remains an intuition in search of a

the strongest case against radical life extension rests on an intuition that still lacks a

principle.

## See also