The Trouble with Kant’s Humanity Formula

Andrew Johnson

It is probably safe to say that, of Kant’s various formulations of the Categorical Impera-

tive, none has been more well-received than the Humanity Formula. “So act that you use human-

ity, whether in your own person or in the person of any other, always at the same time as an end,

never merely as a means” (G 4:429).1 As against Utilitarianism, the Humanity Formula seems,

more clearly than Kant’s Universal-Law Formula, to uphold the widely accepted view that per-

sons have certain inviolable rights. Persons may not be enslaved or raped, they may not be pun-

ished without having committed a crime, no matter how much happiness such actions might

yield others. Prominent Kantian moral philosophers, such as Christine Korsgaard, Allen Wood,

and Alan Donagan, have defended the Humanity Formula as a basic moral principle of theoreti-

cal ethics.2 Moreover, it has frequently provided inspiration for arguments in applied ethics. Ex-

amples include Denis Arnold’s and Norman Bowie’s critique of sweatshops,3 Onora O’Neill’s

argument for famine relief,4 and Barbara Herman’s analysis of sexual objectification.5

According to Kant, the Categorical Imperative is “the supreme principle of morality”

1 All translations of Kant’s moral writings are taken from Immanuel Kant, Practical Philosophy, trans. and ed. Mary

J. Gregor (Cambridge: Cambridge University Press, 1996).

2 See, e.g., Christine Korsgaard, The Sources of Normativity (Cambridge: Cambridge University Press, 1996), espe-

cially pp. 122ff.; Allen Wood, Kant’s Ethical Thought (Cambridge: Cambridge University Press, 1999), pp. 111–55;

Alan Donagan, The Theory of Morality (Chicago: University of Chicago Press, 1977).

3 Denis Arnold and Norman Bowie, “Sweatshops and Respect for Persons,” Business Ethics Quarterly 13 (2003).

4 See, e.g., Onora O’Neill, “Rights, Obligations and World Hunger,” in Poverty and Social Justice: Critical Per-

spectives: A Pilgrimage toward Our Own Humanity, ed. Francisco Jimenez (Tempe, AZ: Bilingual Press, 1987),

pp. 86-100.

(G 4:392), and it is a principle that is supposed to give us guidance regarding, among other

things, the morality of actions. For a principle to qualify as the supreme principle of the morality

of actions, it must, I take it, satisfy three conditions. Firstly, it must be fundamental, in the sense

that it is not derivable from a still more basic principle of moral action. Secondly, it must be

complete, in that it is neither limited to certain spheres of action nor in need of supplementation

by additional moral principles. Finally, it must be plausible, not yielding implications that even

most proponents of the principle would regard as false. In what follows, I focus on these last two

conditions, which I call “the completeness condition” and “the plausibility condition.” My argu-

ment will be that the Humanity Formula does not jointly satisfy both conditions. If it is inter-

preted so as to be complete, it is implausible. If it is interpreted so as to be plausible, it is incom-

plete.

The completeness condition specifies that a supreme moral principle must, at least in the-

ory,6 and without reliance on any further moral principles, be action-guiding in every situation.

(Note that one way a principle can be action-guiding is by implying that an action under consid-

eration is morally permissible, though not morally required.) Kant evidently endorses this condi-

tion himself. He maintains that “there is only a single categorical imperative” and that “all imper-

atives of duty can be derived from this single imperative” (G 4:421). Although he states the Cat-

egorical Imperative in a variety of ways, Kant insists that the various formulations “are at bottom

5 Barbara Herman, “Could It Be Worth Thinking about Kant on Sex and Marriage?,” in A Mind of One’s Own: Fem-

inist Essays on Reason and Objectivity, ed. Louise Antony and Charlotte Witt (Boulder: Westview Press, 1993),

pp. 49–67.

6 The qualification “at least in theory” is supposed to block as a decisive criticism of a consequentialist principle of

rightness the point that we are sometimes unable to determine which action out of the alternative actions has the best

consequences. For obvious reasons, I don’t want in my argument to rely on a stronger necessary condition of ade-

quacy than necessary.

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only so many formulae of the very same law” (G 4:436). As a version of the supreme principle

of morality, the Humanity Formula purports to guide action in any situation in which a moral

agent might find herself. Yet, as I will try to show, there is a whole class of situations (what Kant

calls “imperfect duties”) for which the Humanity Formula cannot properly guide action unless it

is supplemented by some additional moral principle.

The plausibility condition is that a supreme moral principle must not have any implica-

tions that are or would be widely agreed to be false, even by partisans of the principle. For ex-

ample, many philosophy students who initially declare themselves partisans of straightforward

cultural relativism abandon the view once they see that it sanctions the rankest forms of racism

or sexism within deeply racist or sexist cultures. I will make a case that applying the Humanity

Formula to particular types of action yields implications that even most Kantians will concede to

be false.

My argument will also be informed by what I take to be a corollary of the completeness

condition’s requirement of “action-guidingness,” namely, the hermeneutical rule that an inter-

pretation of a vague moral principle should not be framed in terms of concepts that are equally

vague or vaguer. A facetious example will illustrate the point of such a rule. Were we to inter-

pret the Humanity Formula as equivalent to the injunction of 1 Peter 3:11 to “turn away from

evil and do good,” this might inoculate it against any objections. Yet it would render the Human-

ity Formula useless in precisely those cases for which we would like to have a moral principle:

cases in which we are unsure or disagree about what is good and what is evil. In my view, the in-

junction always to treat humanity in persons as an end, never as a means only, is vague and, to

be generally useful, requires interpretation in more specific terms.

This contention requires some defense; not all Kantian ethicists would agree with it.

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Allen Wood, for example, maintains that “[t]he meaning of [the Humanity Formula] is clear and

determinate because the concepts of humanity (or rational nature) and existent end in itself are

both reasonably clear and determinate.”7 If Wood were right about this, we would not be able to

distinguish three possible interpretations of the Humanity Formula on the basis of Kant’s discus-

sion of the false-promising example, whereas in fact we can, as I will presently argue. In addi-

tion, some questions about awkward cases for the Kantian can motivate the impression that the

Humanity Formula is less than fully precise. Does a prostitute treat humanity in her own person

as a mere means? Were families who hid Jews from the Nazis morally prohibited from lying to

Nazi soldiers who came knocking? Does a corporation that pays sweatshop workers the barest

subsistence wage, although it could afford to pay them significantly more, fail to treat them as

ends? Without further analysis of what it is to treat humanity in persons as mere means or as

ends, it isn’t clear what answers the Humanity Formula implies to such questions.

Furthermore, analyzing the Humanity Formula as a requirement “to respect every human

being, oneself or any other, as a rational creature,”8 or always to treat persons with dignity, or not

to interfere with persons’ autonomy, or to treat persons in accordance with rational principles,

does not resolve the difficulty. For intuitions about the nature of respect, dignity, autonomy, and

rational principles will likewise diverge with respect to controversial cases.

In the interests of adding precision to the Humanity Formula’s injunction, we may note

that it lays down two requirements. Firstly, we should not treat humanity in persons as a mere

means; call this the ‘negative requirement.’ Secondly, we should treat humanity in persons as an

end; call this the ‘positive requirement.’ While these two aspects of the Humanity Formula are

not logically equivalent to each other, some commentators have pointed out that there is funda-

7 Op. cit., p. 154.

8 Donagan, op. cit., p. 66.

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mentally just one requirement: to treat humanity (in Kant’s idiosyncratic sense) as an end, with

the requirement to avoid treating humanity as a mere means being a narrower logical implica-

tion.9 I agree that, conceptually, one cannot treat a person as an end and simultaneously treat him

as a mere means. However, I argue in what follows that, when it comes to applying the Human-

ity Formula, the requirement to treat humanity as an end cannot stand alone.

In speaking of humanity as an “end,” Kant is not using the term in its standard sense of a

goal or purpose to be achieved. Ends of this sort Kant regards as subjective ends, whereas human

beings (or at least those possessing practical reason) are objective ends (G 4:431). Objective ends

are ends in themselves, not in the traditional sense of being subjectively valued for their own

sakes, but in the sense of having an inviolable dignity not deriving from subjective human atti-

tudes. Objective ends constitute morally necessary side-constraints on our subjective ends. In

Kant’s words, “a rational being, as an end by its nature and hence as an end in itself, must in ev-

ery maxim serve as the limiting condition of all merely relative and arbitrary ends” (G 4:436).

This passage provides a clue as well to what Kant means by ‘humanity.’ What is morally

crucial about humanity in a person is its identity with—or perhaps inclusion of—the person’s ra-

tional nature, which encompasses the person’s capacity for rational agency. Shortly before Kant

introduces the Humanity Formula, he affirms that “rational nature exists as an end in itself”

(G 4:429). Either this is just a variant formulation of the proposition that humanity exists as an

end in itself, or humanity is a subspecies of rational nature.

However, even assuming we have a clear understanding of the concepts of humanity and

an end in itself, it isn’t obvious what we must do to fulfill the Humanity Formula’s positive and

9 See, e.g., Allen Wood, Kant’s Ethical Thought (Cambridge: Cambridge University Press, 1999), p. 143; and

Thomas Hill, Jr., “Treating Criminals as Ends in Themselves,” Jahrbuch für Recht und Ethik, Vol. 11 (2003),

pp. 19-20.

5

negative requirements. Kant offers some clarification of his positive requirement as it applies to

humanity in others with his beneficence example in the Groundwork. Kant remarks that

[h]umanity might indeed subsist if no one contributed to the happiness of others but yet did not in-

tentionally withdraw anything from it; but there is still only a negative and not a positive agree-

ment with humanity as an end in itself unless everyone also tries, as far as he can, to further the

ends of others. For, the ends of a subject who is an end in itself must as far as possible be also my

ends, if that representation is to have its full effect in me. (G 4:430)

Although Kant places no restrictions in this passage on the ends of others which I am to make

mine, charity demands we interpret the passage quoted above as requiring that we make only the

permissible ends of others our own;10 otherwise the Humanity Formula would have the unaccept-

able implication that we should adopt the nefarious ends of, e.g., thieves, pedophiles, murderers,

and House Republicans. In The Metaphysics of Morals, Kant explicitly issues the needed qualifi-

cation: “When it comes to my promoting happiness as an end that is also a duty, this must there-

fore be the happiness of other men, whose (permitted) end I thus make my own end as well”

(MM 6:388; parenthesis and italics in original; underlining added).11 Kant, who disdains eudai-

monistic ethics (see, e.g., MM 6:377–78), does not operate with a morally sanitized conception

of happiness according to which any action that truly contributes to a human being’s happiness is

morally permissible. Unlike moral requirements, which hold necessarily for all rational agents

10 Charity also demands, of course, that we hold to a manageable number the range of others whose ends we ought to

promote. But this is an exegetical question I shall not enter into here.

11 H. J. Paton is exceptional in recognizing the need for the qualification, noting that “we ought to further the ends of

others only so far as they are not manifestly foolish or incompatible with the moral law” (op. cit., p. 173). However,

he fails to notice the problem of circularity—which I am about to describe—involved in determining whether an end

is “incompatible with the moral law.”

6

who have sensuous natures and thus “inclinations” (Neigungen),12 the ingredients of happiness

are a fundamentally subjective matter. Kant holds that “[i]t is for [others] to decide what they

count as belonging to their happiness” (MM 6:388).

But if the Humanity Formula enjoins us in part to promote the permissible ends of others,

then we need a criterion of their moral permissibility. The needed criterion must come either

from the Humanity Formula itself or from outside the Humanity Formula. If it can come only

from outside the Humanity Formula, then the formula fails the completeness condition. If, on the

other hand, the Humanity Formula can supply the requisite criterion of permissible ends itself,

then it must be through its negative requirement, since the positive requirement is what gives rise

to the need for the criterion of permissible ends in the first place. On this interpretation, the per-

missible ends of others are those the attainment of which does not entail treating any person as a

mere means.13 We could rule out the characteristic ends of thieves, pedophiles, murderers, and

House Republicans as worthy of promotion on the grounds that attainment of these ends entails

using others as mere means. But, as we shall see, this proposal doesn’t lead to a sound Humanity

Formula either, since the formula’s prohibition against using persons as mere means has false

12 Rational agents who do not have sensuous natures are not subject to moral requirements, or duties, because they

necessarily act in accordance with reason and hence morality. The notion of a duty to perform a particular action

makes sense only when an agent has the option of omitting the action. See, e.g., CPrR 5:32.

13 I have heard this interpretation proposed by both Jon Tresan and Luke Robinson in conversation. The idea that an

irreducibly basic requirement of the Humanity Formula is the prohibition against treating humanity as a mere means

cannot, however, be said to be orthodox among Kant commentators. Both Allen Wood (op. cit., p. 143) and Thomas

Hill, Jr., (“Treating Criminals as Ends in Themselves,” Jahrbuch für Recht und Ethik, Vol. 11 [2003], pp. 19-20),

for example, take as basic the injunction always to treat humanity as an end, with the proscription against treating

humanity as a mere means being just a logical implication. Wood puts it starkly: “the phrase ‘never merely as a

means’ actually plays no role whatever in the actual content of FH” (ibid.; italics in original).

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implications on textually grounded interpretations.

What is it to treat a rational agent as a mere means? Kant offers some clarification in his

Groundwork examples of the suicide and the false promiser. Given the controversial nature of

Kant’s rather sweeping disapproval of suicide, I shall consider only Kant’s explanation of how

the false promiser treats (the humanity of) the promisee as a mere means. On this question, Kant

explains that

as regards necessary duty to others or duty owed them, he who has it in mind to make a false

promise to others sees at once that he wants to make use of another human being merely as a

means, without the other at the same time containing in himself the end. For, he whom I want to

use for my purposes by such a promise cannot possibly agree to my way of behaving toward him,

and so himself contain the end of this action. This conflict with the principle of other human be-

ings is seen more distinctly if examples of assaults on the freedom and property of others are

brought forward. For then it is obvious that he who transgresses the rights of human beings intends

to make use of the person of others merely as a means, without taking into consideration that, as

rational beings, they are always to be valued at the same time as ends, that is, only as beings who

must also be able to contain in themselves the end of the very same action. (G 4: 429–430)

Ironically, Kant’s explanation may raise as many questions as it answers. It contains, at a

minimum, three possible analyses of what it is to treat humanity in another as a mere means.14

These analyses involve, respectively, the other’s not actually sharing the agent’s end, the other’s

not possibly sharing the agent’s end, and the other’s not possibly agreeing to his treatment by the

agent. The analyses aren’t mere exegetical possibilities, but have been employed, as I will illus-

trate, by leading Kantian ethicists. We need not determine which of the analyses is definitive. For

every one of them, I hope to show, spells trouble for the Humanity Formula.

The first possible analysis is based on Kant’s assertion that the lying promiser is using the

14 “At a minimum,” since further possibilities arise from combining the three basic possibilities in various ways.

8

promisee without the promisee “at the same time containing in himself the end.” It suggests the

following principle:

(NR1) Action a treats (the humanity in) person P as a mere means if and only if a has end

e, a cannot bring about e without affecting P, and P does not hold e.

Two elements of the analysans, “a has end e” and “P does not hold e,” are straightforward

enough; they convey merely that the action in question aims at an end that the recipient of the ac-

tion does not actually hold. The third element, “a cannot bring about e without affecting P,” may

seem a needlessly convoluted variant of the more straightforward “a affects P.” But the latter,

unlike the former, has the implausible implication that it is possible to treat as mere means those

inadvertently affected by an action.15

Allen Wood affirms an understanding of the negative requirement very much like (NR1).

He explains how Kant’s application of the Humanity Formula to the false-promising case clari-

fies Kant’s earlier evaluation of the case according to the Formula of the Law of Nature:

If … the giving and accepting of a promise requires the promiser and the promisee to share their

ends, then it is clear why the promises falling under U2 [which states that “[i]t is a universal law

of nature that when anyone believes they are in need of money, they will borrow it and promise to

15 In fact, I believe more needs to be said here about the way a affects P. Consider, for example, a factory that emits

pollution into the environment for the end of minimizing costs, though the factory managers know that the pollution

will likely be a contributing factor to a number of premature deaths. The managers might claim that their action of

polluting doesn’t run afoul of (NR1), since it is possible that their polluting could bring about the end of minimizing

costs without having any adverse health effects on human beings (as would be the case if the people exposed to the

pollution had exceptionally hardy constitutions). Clearly this isn’t the result a Kantian should want. But I don’t have

the space to explore this angle here.

9

repay it without having any intention to do so”16] would be impossible, since they preclude such

sharing.17

The salient moral fact on the present analysis is that the promisee does not in fact hold

the end of the lying promiser, whatever end the lying promiser is aiming at. But if this is what it

is for one person to treat another as a mere means, the Humanity Formula is much too restrictive,

for it would forbid our treating others justly when they don’t hold the end of being treated justly.

It would be wrong to deny an unqualified job applicant a job if she doesn’t hold the end of hav-

ing the job performed by the most qualified applicant, wrong to fail the “F” student who wants a

better grade than he is entitled to, and wrong to punish former presidents and vice-presidents for

violations of domestic and international law when they believe they should be able to act with

impunity.

The next two analyses of treating humanity as a mere means are rooted in Kant’s claim

that the promisee “cannot possibly agree to my way of behaving toward him, and so himself con-

tain the end of this action” (G 4:429–30). Christine Korsgaard takes this passage as the basis of

her exegesis of the Humanity Formula’s negative requirement, which entails what Kant calls

“perfect duties,” or duties which allow “no exception in favor of inclination” (G 4:421n.). The

phrases “cannot possibly agree to my way of behaving toward him” and “cannot … himself con-

tain the end of this action” yield, in Korsgaard’s words, “a test for perfect duties to others: an ac-

16 Op. cit., p. 87.

17 Ibid., p. 148. In a striking coincidence, Wood goes on in the next sentence to reproduce Kant’s shift from an actual

sharing of an end to a possible sharing (“cannot consent”) of it. The shift doesn’t necessarily indicate an inconsis-

tency. It could be that the impossibility of consenting to being treated in a certain way is being cited as evidence that

the recipient of the action does not actually share the end of the agent.

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tion is contrary to perfect duty if it is not possible for the other to assent to it or to hold its end.”18

Korsgaard conflates the meanings of these two phrases, although they are in fact importantly dis-

tinct. The expression “my way of behaving,” contained in the first phrase, refers to the action I

perform as a means to my end, whereas the second phrase refers explicitly to my end. Which ex-

pression is more essential to Kant’s explanation of the wrongness of false promising?

Suppose for the sake of argument that the more fundamental point for Kant is that the

promisee cannot hold the end of the lying promise. If so, Kant cites the impossibility of the

promisee’s agreeing with the action as evidence for this point. Then we have the following anal-

ysis of what it is to treat humanity in a person as a mere means:

(NR2) Action a treats (the humanity in) person P as a mere means if and only if a has end

e, a cannot bring about e without affecting P, and P cannot hold e.

(NR2) represents an improvement over (NR1) insofar as (NR2) does not render certain kinds of

treatment immoral simply because the recipient of the treatment does not share, however unrea-

sonably or immorally, the end of the treatment. (NR2) does not, for instance, exempt lawbreakers

from punishment simply because they do not share the ends of the punishment. A lawbreaker

can, in principle, share the end society has in punishing him. Yet, whereas (NR1) results in too

restrictive a Humanity Formula, (NR2) makes it too permissive. For it is possible for those un-

avoidably affected by even the most immoral actions to hold the ends of those actions. The end

of the car thief may be to enjoy the full-time use of my car, and it is quite possible for me to

share that end, as I would if I decided to give my car to him. The end of the rapist may be sexual

gratification, and it too is an end it is possible for the rape victim to share (though not, of course,

18 Christine Korsgaard, “The Right to Lie,” in her Creating the Kingdom of Ends (Cambridge: Cambridge University

Press, 1996), p. 138. Korsgaard’s statement of the phrases in question diverges slightly from mine, as she uses a dif-

ferent translation.

11

qua rape victim). The end of the false promiser may be to pay off a debt or make a purchase, and

there is nothing in principle precluding the promisee from holding this end as well.19

Korsgaard would take issue with this point. She argues that, when you make a false

promise, the promisee cannot in fact hold the end of the promise:

In cases of violation of a perfect duty, lying included, the other person is unable to hold the end of

the very same action because the way that you act prevents her from choosing whether to contrib-

ute to the realization of that end or not. Again, this is obviously true when someone is forced to

contribute to an end, but it is also true in cases of deception. If you give a lying promise to get

some money, the other person is invited to think that the end she is contributing to is your tempo-

rary possession of the money: in fact, it is your permanent possession of it.20

The disagreement between Korsgaard and myself raises the question of what is to count as the

end of an action. So far I have spoken of the end of an action as if it were unproblematic that ev-

ery (intentional) action has one and only one end. In fact, an action can have any number of ends.

For instance, a person might enroll in college as a means to the ends of becoming a doctor, de-

veloping a deeper understanding of American history, and livening up her social life. All of these

ends might in turn be means to the more final end of her happiness. Hence, even if Korsgaard is

right that the promisee in Kant’s example cannot hold the end of the promiser’s permanent pos-

19 Thomas Hill Jr. attempts to circumvent this problem by adding further conditions for the kind of possibility in

question. We conform to the Humanity Formula “by restricting our ends and means to those that anyone affected by

us ‘could share’ at least in the sense that they could rationally and reasonable [sic] endorse them” (op. cit., p. 24).

While there may be philosophical merit to this proposal, it strikes me as a problematic (route of) interpretation of the

Humanity Formula, given that Kant in the Groundwork evidently thought it could be applied to specific actions

without need for Hill’s criteria of rational and reasonable endorsement. In fairness to Hill, the paper in question does

not claim “strict fidelity to [Kant’s] views” (ibid., p. 25).

20 Op. cit., p. 139–40.

12

session of the promisee’s money, her interpretation of the Humanity Formula will not establish

that it is a sound moral principle until she offers a non-ad hoc reason for fixing on this end to the

exclusion of other ends of the promiser that the promisee can hold.

But I don’t believe Korsgaard is actually right about this. Suppose, in order to obtain a

$100 loan from me, you make a false promise to pay it back; hence you have the end of taking

permanent possession of my $100. Suppose, in addition, that I, ever a sucker for your counterfeit

charms, want to give you the $100 as a gift, but don’t tell you yet, saving the news as a surprise

for your birthday next week. Then we both actually do have the end of your having permanent

possession of my $100; a fortiori we can hold the same end. It follows, according to Korsgaard’s

interpretation of the Humanity Formula, that you do me no wrong in giving me the false promise.

This is not the result we should want.

Given the shortcomings of (NR2), then, let us assume that the morally relevant and more

fundamental feature of the false promise case is that the promisee “cannot possibly agree to [the

promiser’s] way of behaving toward him” (G 4:429–30). What Kant evidently has in mind is the

logical impossibility of agreeing to receive a false promise in a particular case. It is logically im-

possible to make a promise to someone who rejects it out of hand, and someone who knows a

promise is false will reject it out of hand (G 4:422). Korsgaard endorses this interpretation of the

negative requirement too, as she doesn’t distinguish the impossibility of a patient’s agreeing to

an agent’s way of treating him from the impossibility of the patient’s holding the agent’s end.

She describes a case very similar to the one I just considered. However, in her case, we are to

imagine that I somehow know from the beginning that your promise to repay the loan is a false

one, but that I nevertheless want you to have my money. In that event, she rightly points out,

“[t]he nature of the transaction is changed: now it is not a promise but a handout.”21 Onora

21 Op. cit., p. 139.

13

O’Neill is another prominent proponent of this understanding of the Humanity Formula’s nega-

tive requirement.22

We can analyze the interpretation now under consideration as follows:

(NR3) Action a treats (the humanity in) person P as a mere means if and only if a cannot

bring about its end without affecting P, and there is some true description of a under

which it is impossible for P to agree to a (other than the description “P did not actu-

ally agree to a”).

The latter clause in the analysans (before the parenthesis) is intended to circumvent a kind of

problem of relevant description. A theft can also be truly described as an “appropriation”; a rape

is also an act of sexual intercourse. And there is no contradiction involved in a person’s agreeing

to another’s appropriation of her property or to sexual intercourse. By specifying that “there is

some description of a under which it is impossible for P to agree to a,” (NR3) ensures that an ac-

tion cannot fulfill the Humanity Formula’s negative requirement merely through redescription.

(NR3) properly deems actions such as theft or rape treatment as a mere means, because it

is impossible for the victim of such an action to agree to it without undermining the action’s sta-

tus as a theft or rape. Yet (NR3) results in false positives. Suppose a self-disrespecting wife

agrees to her husband’s abuse of her, which he engages in for the end of venting his frustrations.

Given her actual agreement to this treatment, I see no true description of it under which it is im-

possible for her to agree to it. Therefore, by (NR3), the husband does not treat his wife as a mere

means. In reality, however, he clearly does. The same problem will attend any immoral treatment

of one person by another where the object of the treatment agrees to be so treated.

My argument has been an argument by elimination, with the twist that I claim to have

22 Onora O’Neill, “Universal Laws and Ends in Themselves,” in her Constructions of Reason: Explorations of

Kant’s Practical Philosophy (Cambridge: Cambridge University Press, 1989), pp. 138-39.

14

eliminated all the alternatives. None of three reviewed understandings of the Humanity For-

mula’s negative requirement, I have contended, renders this requirement a tenable moral princi-

ple. And if this entailment of the Humanity Formula is untenable, then so must be the Humanity

Formula itself. The potential pitfall of this argument is one that attends any argument by elimina-

tion: the best alternative might have gone unconsidered. Or perhaps a construal of the positive re-

quirement can be offered that overcomes my objection that it lacks a criterion of permissible

ends; this would obviate any need for the negative requirement. I would be happy if either of

these lines of response to my critique turned out to be correct. It would be no small consolation

to think that, in the countless hours I have spent poring over Kant’s excogitations about humanity

as an end in itself, I was imbibing truth. After all, it’s something of a stretch to maintain that

reading Kant is valuable for its own sake.

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