1. Kant on Marriage

Kant’s sexual ethics and conception of marriage are of great significance for the emerging scholarly debate on the history of philosophical reflection on same-sex marriage, as Kant explains the ethical rationale for marriage ‘without appealing to either religious tradition or legal precedent’ (Altman Reference Altman2011: 140), and he offers ‘a secular argument for an institution of marriage’ (Wilson Reference Wilson2004: 121). However, his discussion of sex and marriage is at times phrased in crude ways. This has led to much ridicule, such as Paul Guyer’s (Reference Guyer2006: 276) quip that ‘Kant’s views about sex are, to put it mildly, bizarre, in part at least either the views of a bachelor or the views that made him a bachelor’. Kant does largely abstract from elements that we today think of as important to marriage, such as emotional investment.Footnote ² His discussion was also unusual in his own time, since his conception of marriage is ‘radically detraditionalized’ (Kuster Reference Kuster2011: 338).Footnote ³ Kant is interested in the question of why marriage is legally and morally significant, and he believes that neither emotions, nor nature, nor tradition, nor religion (the traditional sources of the value of marriage) can provide an answer. His sterile and technical discussion might seem off-putting at first, but it does express Kant’s earnest attempt to discover what makes this aspect of human community and interaction morally and legally significant. His argument for why there must be marriage draws on many ideas that would require detailed discussion and critical scrutiny. In this section, I will summarize Kant’s view of the matter only insofar as they concern our main goal.

For Kant, the reason why we need marriage at all is that sex is morally problematic. When having sex ‘a human being makes himself into a thing, which conflicts with the right of humanity in his own person’ (6: 278.8–9). When having sex, we use a person as ‘a consumable thing’ (6: 360.5) or as an instrument for satisfying desires and obtaining pleasure. Sex for Kant is a form of objectification since it entails that we make use of another for our pleasure and let another make use of ourselves in turn. Kant worries that this violates our and our partner’s humanity.Footnote ⁴ If we use a person as a means for sexual gratification, we lack proper regard for her as an end in herself or as something that is not exchangeable and not merely physical, and we lack proper regard for ourselves if we allow others to use us in this way or if we use ourselves in this way (cf. Groundwork, 4: 429.10–12).

To better understand the problematic nature of sexual desire, let us briefly look at Seiriol Morgan (Reference Morgan2003: sec. 3), who is sympathetic to Kant’s analysis. He argues that there are two problems that Kant has with sexual desire. The first is that, when having sex, a human being surrenders her humanity to her animal instincts and acts like a mere animal or even ‘makes himself into a thing’ (see above, as well as 6: 425, 27: 385). The second, which Morgan takes to represent a deeper insight into the nature of sexual desire, is that Kant is in general concerned with our tendency to subjugate or dominate others. This tendency is a specifically human one, rooted in our competitive human nature and our unsocial sociability (7: 268.14–274.18; ‘Idea for a Universal History’, 8: 20.30), which drive us to crave other human beings’ esteem as well as to impose our wills upon them (7: 273.16–34). Kant was a pessimist about the general human drive to assert oneself over others. Sexual desire can easily be affected by this tendency, as it is a central element of our self-constitution and sex is a way of interacting that leaves both partners vulnerable to abuse, exploitation and domination. Sex thus can become a field of domination and subjugation, unless proper protections for all involved obtain. Morgan thinks that mutual consent is not sufficient protection in all cases. His account helps us make sense of Kant’s negative attitude to sex. The threat of domination and subjugation is a much more immediate moral concern for us today than the supposedly animalistic nature of sexual desires.

Sex for Kant leaves us with the problem of how we can protect ourselves and others from domination or how we can ‘treat each other with the dignity we deserve as rational persons when, in sexual terms, we are out to use each other for the sake of some end, be it our own pleasure or reproduction’ (Altman Reference Altman2010: 312). It is important to note that finding a way to deal with the moral problem of sex is not optional for Kant. Despite its inherent danger, sex serves the natural end of the perpetuation of the human species.Footnote ⁵ A human being without sexual impulses would even be ‘an imperfect individual, in that one would believe that he lacked the necessary organs, which would thus be an imperfection on his part, as a human being’ (27: 385.11–13).

Kant believes that only in the context of marriage can two people have intercourse in which neither of the spouses is ‘dehumanized through the bodily use that one makes of the other’ (6: 359.31–2) or without there being the acute danger of one dominating the other. The reason that Kant gives is that in a marriage contract ‘one person is acquired by the other as if it were a thing, the one who is acquired acquires the other in turn: for in this way each reclaims itself and restores its personality’ (6: 278.6–22). Whilst this sounds extremely technical, Kant here does in fact outline a conception of marriage based on equality.

Three things are important for our purpose here. First, Kant talks about marriage as a form of acquisition. This manner of speaking is odd, given that we usually acquire objects, not persons. However, for much of its history marriage was seen as an (economic) transaction where fathers negotiated their daughters’ coming into possession by would-be sons-in-law. Furthermore, in the Doctrine of Right, Kant models rightful relationships in general on the paradigm of object possessionFootnote ⁶ and he thinks of marriage as a form of joint possession of material goods as well as of each other as persons. We will discuss this more extensively in sections 3 and 5. Second, the process Kant describes is reciprocal. I give myself to the other and the other gives herself to me and hence we both receive ourselves back.Footnote ⁷ Third, the process would not be possible, i.e. not result in a rightful marriage, if we could not acquire each other fully. If there is something my prospective spouse has or owns that I cannot own, the reciprocal giving would only be partial. My spouse would then acquire me fully but I would not fully acquire my spouse, and this means that I would not receive myself fully back in turn. Reciprocal and full possession of each other requires equality. I will argue in section 3 that we should understand the equality in question here as equality between legal persons meaning that two people share each other’s rights. Persons who cannot acquire each other reciprocally and fully are, according to Kant, banned from marrying each other.

If both spouses have acquired each other fully and thus received themselves back fully, marriage secures the spouses’ humanity, since it allows ‘possession of an external object as a thing and use of it as a person’ (6: 276.19–20, see also 27: 639.12–18), i.e. in marital intercourse safeguards are in place that protect each other, even if spouses engage in activities that make them vulnerable to domination or abuse by each other. A number of recent interpretations help us understand why Kant believes that mere consent is not sufficient for this purpose. Lara Denis argues that, if sexual unions were without legally enforceable rights of the respective partners against each other, then ‘partners would lack the security and the implicit recognition of equality that legal marriage provides’ (Denis Reference Denis2001: 12). Along the same lines, Helga Varden argues that ‘there must be a public person with the appropriate standing to adjudicate disputes amongst adults sharing a domestic sphere’ (Varden Reference Varden2007: 206) and for this marriage needs the state to act as a ‘civil guardian over domestic relations, the public adjudicator in conflicts, and as the guarantor of private property rights’ (213). I only fully recognize my partner as worthy of respect if I acknowledge the authority of an impartial arbiter who can with external force protect my partner from domination and subjugation.

Kant’s idea that any kind of intercourse is dangerous or even morally wrong unless the partners are married is admittedly excessively moralistic whether or not marriage is open to same-sex couples.Footnote ⁸ I will come back to this point towards the end of the article. What we should take away from Kant’s conception of marriage so far is that Kant believes that equality between partners is a constitutive feature of marriage. Marriage between unequals would enshrine already existing inequalities into a contract and thus pose a serious peril for the weaker partner to be dominated by their spouse. This contractually sanctioned inequality would make marital intercourse presumably even more dangerous for the weaker party than extramarital intercourse would be.

2. Kant on Same-Sex Marriage

In his Metaphysics of Morals as well as in some of the lecture notes Kant articulates a number of moral objections against same-sex intercourse. He dismisses same-sex intercourse as ‘unnatural’, exhibiting ‘unmentionable vices’, and he states that ‘there are no limitations or exceptions’ to this repudiation (6: 277.17–21). He also ranks masturbation, same-sex intercourse and bestiality as more despicable even than suicide (6: 425.6–36, 27: 391.6–392.5, 642.3–15).Footnote ⁹ Without doubt, Kant still shared many of the traditional views of his time concerning sex, marriage and gender. He once defines marriage as ‘the union of two persons of different sexes for lifelong possession of each other’s sexual attributes’ (6: 277.25–6, my emphasis). That marriage has to be between different sexes is, however, a superficial element of his account, as I will argue in this section.

Matthew Altman (Reference Altman2010, Reference Altman2011) has recently made a compelling case that, given Kant’s views on sex and marriage, the Kantian framework allows for and even requires same-sex marriage, ‘despite [Kant’s] protestations to the contrary’ (Altman Reference Altman2011: 158). I will now briefly rehearse four reasons why on Kant’s framework marriage should be open to same-sex couples.Footnote ¹⁰ I will restrict myself to brief summaries of arguments, since the focus is not to establish that Kant’s framework is open to same-sex marriage, but that it might not be to heterosexual marriage.

(1) Altman’s (Reference Altman2011: 151) most fundamental argument in favour of same-sex marriage in Kant’s framework is that ‘Kant merely assumes a close link between our natural ends and the categorical imperative without showing how or why contradicting our natural ends would necessarily amount to irrational actions’.Footnote ¹¹ Kant seems to have admitted natural law theory into his ethics insofar as he concedes that ends that we have by nature are morally significant. He explicitly criticizes such an approach in the Groundwork (4: 441.25–445.15). Appeal to natural purposes, such as procreation, alone cannot establish duties, since duty is rooted in formal principles of the will. Kant’s moral dismissal of same-sex intercourse is incompatible with a fundamental assumption of his own ethical theory.Footnote ¹²

(2) Even if we admit the existence of morally significant natural ends, same-sex intercourse would not thwart the natural end of procreation – it simply does not advance it.Footnote ¹³ It is not clear what Kant regards as the appropriate attitude to the end of procreation. He states that ‘one may not, at least, act contrary to that end’ (6: 426.3–4). Kant certainly does not think that we have to maximize the promotion of this end or promote it to the detriment of other ends, since we have a number of natural as well as other ends, some of which are even obligatory.Footnote ¹⁴ He would not see it as morally problematic if, on many occasions, we pursue ends other than procreation. There could be cases in which disregarding a natural end amounts to undermining my agency. In these cases, it might become a moral duty that I pursue this end at least to such an extent that my agency is secured. However, same-sex intercourse does not undermine anyone’s agency and is not any more incapacitating than different-sex intercourse (Altman 2010: 324; Reference Altman2011: 153).

(3) We consider the maxim to procreate as a ‘coordination maxim’ (Altman Reference Altman2011: 153). Not everyone needs to engage in procreation and certainly not all the time. If the population is increasing or remains steady without your contribution, there is no need for you to procreate. Altman’s point can be exegetically strengthened by paying close attention to how Kant phrases the natural end of procreation: it is not simply procreation that is a natural end but ‘begetting and bringing up children’ (6: 277.26–7; my emphasis). Bringing up children is a contribution to the survival of the species and something people can do without engaging in any potentially procreative sex. Those who engage in non-procreative sex are still able to do their part to secure species survival, for instance by raising foster children or, more indirectly, by paying taxes which then subsidize public childcare, schools, etc.Footnote ¹⁵

Kant’s negative attitude towards same-sex intercourse is at least partly the result of his conviction that it cannot fulfil the important function of procreation.Footnote ¹⁶ Nonetheless, as I argued, same-sex couples can perform important functions to further the natural goal of species survival. Furthermore, it is not even ‘requisite for human beings who marry to make [the end of begetting and bringing up children] their end in order for their union to be compatible with right’ (6: 277.29–30). This is so for two reasons. First, if procreation was a prerequisite for marriage, then ‘marriage would be dissolved when procreation ceases’ (6: 277.30–2), whereas Kant thinks that marriage is a ‘lifelong’ union (6: 277.25) even if one or both of the spouses become infertile (6: 279.29–35). Second, institutions and laws can only police external behaviour, not the adoption of ends (6: 381.30–5). Adopting certain ends can therefore not be required for marriage as we find it discussed in Kant’s political philosophy.

(4) Kant does not object to different-sex marital intercourse rooted entirely in the desire for pleasure. What matters for Kant is not the naturalness or unnaturalness of the act, nor whether a couple intends to procreate, but whether the partners have bound themselves to each other in a way that ensures mutual respect (Altman Reference Altman2011: 155; see 6: 277.33–278.4, 426.1–32, 27: 639–40). Once the danger of objectification is dealt with, non-procreative sex is permissible. ‘The irony, then, is that it is not the immorality of homosexuality that precludes marriage; rather, not having marriage available to homosexuals makes homosexual unions immoral’ (Altman Reference Altman2011: 161).Footnote ¹⁷

Kant’s teleological assumptions contradict central elements of his ethical theory; and even with these assumptions in place those who do not engage in procreative intercourse can still further the survival of the species. Furthermore, Kant does not object to purely recreational different-sex marital intercourse, and there is no rational grounds on which he could object to recreational same-sex marital intercourse. In fact, his conception of the moral dangers of intercourse, such as instrumentalization and domination, requires that same-sex intercourse take place within marriage.

3. Kant on Marriage between Equals

In the wake of the fourth argument presented in the previous section, Altman (Reference Altman2011: 156) remarks that to answer the question of what forms of sexual relations should enjoy a special legal status ‘Kant focuses entirely on whether the union would be between equals’. This is so because:

I believe that Altman is right, but that his defence of same-sex marriage has consequences he himself does not see. In this section, I will show how the notion of equality between sexual partners functions for Kant as a criterion for rightful marriages. In the next section, I will argue that men and women, according to Kant, are rarely if ever equals.

In §26 of the Metaphysics of Morals, titled ‘Marriage Right’, Kant claims that ‘the relation of the partners in a marriage is a relation of equality of possession, equality both in their possession of each other as persons … and also equality in their possession of material goods’ (6: 278.24–9; see also 27: 388.28, 390.20–1).Footnote ¹⁸ This is a crucial idea for my argument and we need to understand better the notion of equality at play here.

It is relatively uncontroversial what equality of possession of material goods means. the respective possessions of both parties become part of one and the same household and hence joint property. The possession or acquisition of each other as persons, however, is more difficult to understand. ‘Person’ for Kant is a moral term. Personality is an agent’s source of moral imputability (6: 26.10–11). It is unclear, however, what ‘possessing someone else’s source of imputability’ could mean. Kant hardly could have thought that I can have someone else’s actions imputed to me. We can rule this meaning of ‘person’ out in the context of Kant’s discussion of marriage. ‘Person’ is also juridical terminology. Kant discusses marriage as a part of the ‘rights to a person akin to rights to a thing’ (auf dingliche Art persönliches Recht, 6: 276.17). In the context of marriage, ‘person’ is best understood as referring to the legal status of an agent, or her rights.

We have already seen (section 1) that Kant models legal relationships on possession and acquisition. In the context of marriage, we can think of possessing someone as a person as a form of sharing in that person’s rights, just as equality of possession means that I can make use of the other person’s property as if it were mine (and in fact it is). Whilst I can of course not possess a right in the same way as I possess an object, I can share my partner’s rights in the sense that I am allowed to do what she does, because I too have these rights. If I have a right my partner cannot share in, I cannot but withhold something from her in the act of mutual giving that is required for marriage to be rightful. The reciprocity of marriage, that I give myself entirely to the other and that I receive myself back entirely, would not obtain, since there would be an insurmountable difference (something I cannot give to my partner) between us.

Notably, the above-quoted passage about equality between spouses is descriptive: it merely states what the relationship is between spouses who enter into a rightful marriage. Kant also intends equality between prospective spouses as a prescription or as a necessary condition for rightful forms of marriage. This becomes clear when he argues in §26 that morganatic marriages (Ehe von der linken Hand) do not constitute rightful marriages (6: 279.12–16; see also 27: 642.23–6). Morganatic marriages are between people from different social ranks or classes,Footnote ¹⁹ specifically between royalty and commoners. The class difference prevents the passage of certain rights, titles and privileges of the one to the other and to any children born of the marriage. The notion of morganatic marriage is strange to us today, since it presupposes a relatively fixed system of classes defined by family lines. Kant’s dismissal of the possibility of such marriage expresses the concern that there can be insurmountable power differences between people. Due to these differences one party can only acquire the other party on the cheap, i.e. without transferring all rights to the other party.Footnote ²⁰ Kant’s dismissal of morganatic marriage can be understood as socially conservative and intended to reinforce social boundaries. Alternatively, it can be understood as expressing concern for the role of women within marriage, since morganatic marriages standardly featured the husband in the more powerful position (see 27: 641.3–6).

In any case, Kant’s dismissal of morganatic marriage is evidence that he believed equality to be a condition of marriage.Footnote ²¹ It also shows that we should understand the equal possession of each other as persons as the requirement that couples are able to acquire each other’s rights and maybe even certain aspects of their social status insofar as they impact an agent’s legal standing.Footnote ²² The problem with morganatic marriage is that one of the parties is unable to acquire the other’s rights in part or in full. My main argument in this article can be put thus: given Kant’s conception of the sexes, different-sex marriage resembles morganatic marriage and should hence be as problematic for Kant. I do put a lot of emphasis on morganatic marriage for my argument, but I think that what Kant says about it is in line with and follows from his notion of equal possession of each other as persons. We should therefore not consider his remarks ad hoc.

It should be noted that morganatic marriage is not merely marriage between persons of different rank, but marriage that retains that difference in rank. In rejecting morganatic marriage, Kant was not necessarily arguing that no persons of different rank should marry at all. It might still be possible for two people of different social and legal standing to marry each other if the more privileged partner renounces his privileges. However, there might be privileges that, unlike certain royal titles and claims to inheritance, cannot be renounced voluntarily, such as the right of full citizens to vote or to participate in public affairs (see section 4). Even if someone were not to exercise their rights, he would still have them, he could choose to exercise them and they would constitute something their partner, if she lacks these rights, cannot possess.

Directly following his discussion of morganatic marriage, Kant in the same paragraph makes clear that the abstract legal equality that marriage requires need not preclude embodied and lived inequalities within marriage. The husband ‘is to be [the wife’s] master (he is the party to direct, she to obey)’ (6: 279.17–19), and Kant acknowledges a supposed ‘natural superiority of the husband to the wife in his capacity to promote the common interest of the household’ (6: 279.22–3). Within marriage one person has to be subjugated to the other (7: 303.15–17), an arrangement that is supposedly advantageous to both parties (7: 309.29–310.9, 27: 50.12–34). It is significant that these passages speak of inequality within marriage and with respect to the capacity to make decisions, not as a prerequisite for marriage. Kant here does not talk about legal inequality or inequality preceding marriage. As we saw, he excludes certain couples from marriage on account of forms of insurmountable legal inequality prior to a potential marriage. However, once the marriage contract is established there can be (and maybe must be) inequality between the spouses on account of different cognitive abilities, interests, societal norms, etc.Footnote ²³

In addition, Kant of course does not require that even prior to marriage spouses share literally everything. There can be inequality between them in terms of intelligence, physical attributes, level of education and prerogatives acquired as a result of education. A lawyer’s spouse may not practise law just because he is married to a lawyer. He can practise law if he successfully passes the bar exam. Prerogatives acquired via special education and training must be excluded from what defines equality between persons for the purpose of marriage.

As we have seen, inequality of a certain kind makes couples ineligible to marry on Kant’s conception of a rightful marriage. The case of morganatic marriage also shows that equality of possession cannot just mean that spouses have rights to each other that exclude everyone else, specifically to the exclusive use of their partner’s sexual organs.Footnote ²⁴ Morganatic marriages (as well as incestuous relationships between parents and children) can be monogamous and exclude third parties, yet Kant believes that they do not satisfy the requirements for a rightful marriage. Marriage must do more than just assure the spouses of the exclusivity of intercourse. It must be based on a certain form of equality, namely, equality as persons or legal equality.

As I argued in section 1, the requirement that there be equality between spouses is an essential element of Kant’s account. Marriage is supposed to function as a safeguard, and it can only do this effectively if I give myself entirely to my partner, my partner does the same, and each of us thus receives ourselves back entirely. If I have a right that my partner cannot share, the process cannot be fully reciprocal, and my partner is not protected in the same way I am.

4. Kant on the Differences between Men and Women

According to Barbara Herman (Reference Herman, Antony and Witt1993: 54), Kant might be the modern moral philosopher feminists find most objectionable.Footnote ²⁵ This is unsurprising as Kant claims that men and women are not even ‘of the same kind’ (‘Observations on the Beautiful and the Sublime’, 2: 228.34) and he calls women a ‘domestic animal’ (Hausthier, 7: 304.12). It is, though, difficult to determine how much philosophical weight to place on Kant’s scattered sexist remarks. They mainly provide evidence that he was unable to distance himself from the prejudices of his time. He certainly bought into a highly gendered conception of human beings. Some of his feminist critics even allege that Kant believes that women lack something fundamental for being a full human being, such as rationality or moral agency.Footnote ²⁶ Different-sex intercourse should then rather be described from a Kantian perspective as a form of bestiality, and thus could not possibly take place within the union of marriage.

However, it is not clear that Kant regards women as lacking rationality or moral agency, and we must now look at his comments about the differences between men and women in detail to understand how fundamental and deeply rooted they are. There are two areas of potential inequality that are relevant for us. The most important is that of (i) legal inequality, on which I will draw for my argument in the next section. Here I will also briefly discuss (ii) moral inequality, since some interpreters believe that this is the most fundamental form of gender inequality in Kant.

(i) Since Kant discusses marriage primarily as a legal institution, legal inequality is the kind of inequality that is most immediately relevant to the marriage contract. Women, Kant believes, lack ‘civil personality’ (6: 314.32) or ‘civil independence’ (6: 315.5). This makes them merely passive citizens (6: 314.17–25). Active citizenship means that one can participate in the organization of government affairs, introduce laws and vote on them (6: 315.6–22). Women share the status of being merely passive citizens with many men: apprentices, domestic servants, minors, private tutors and in general ‘anyone whose preservation in existence (his being fed and protected) depends not on his management of his own business but on arrangements made by another (except the state)’ (6: 314.29–31). Kant’s distinction between active and passive citizenship based on whether one is financially dependent on another person is certainly peculiar. What is important for us is that all the examples Kant gives of merely passive citizens are of particular occupations – except in the case of women, where the occupation seems not to matter.Footnote ²⁷

In the Anthropology, Kant calls the state of merely passive citizenship immaturity (Unmündigkeit): the ‘(natural or legal) incapacity of an otherwise sound human being to use his own understanding in civil affairs’ (7: 208.34–5). This state can be based on age or legal arrangements. The latter is called ‘legal or civil immaturity’ (209.2). Women of all ages are in a state of legal immaturity.Footnote ²⁸ Husbands are their wives’ ‘natural curator’ (209.5), since women cannot ‘defend their rights and pursue civil affairs for themselves, but only by means of representation’ (209.11–13). Here women are characterized with regard to legal affairs as inferior to men before marriage as well as within marriage. However, immediately after denying women full citizenship in the Metaphysics of Morals Kant concedes that: ‘[t]his dependence upon the will of others and this inequality is, however, in no way opposed to their freedom and equality as human beings’ (6: 315.6–8). It is unclear whether Kant believes that all passive citizens are equal to active citizens as human beings, or whether some humans can, so to speak, be more human than others. The latter is strongly suggested when Kant speaks of the ‘natural superiority of the husband to the wife in his capacity to promote the common interest of the household’ (6: 279.22–3). It is important here that this superiority is said to be natural, i.e. not merely a result of non-ideal legal arrangements.

There are two very different ways to understand Kant’s claims about legal inequality between men and women. One is that they are intended as descriptions of the social implications of the natural inferiority of women. The other is that Kant here describes inequalities that only exist in non-ideal social settings, and that these inequalities can be overcome through social progress. Kant wavers between the idea that gender inequality is due to women’s natural and necessary inferiority, and the idea that women’s state of immaturity is socially constructed and can and should be exited. In what follows, Kant’s claims about gender inequality lending themselves to the latter interpretation will be of central significance for my argument, as they do not hinge on the sexist assumption that women are naturally inferior.

(ii) The notion that for Kant women do not even count as moral agents and as fully rational is fuelled mainly by his early Observations on the Feeling of the Beautiful and Sublime from 1764 and his Remarks on the Observations on the Feeling of the Beautiful and Sublime from around the same time. In the former, Kant claims that women will avoid evil not because it is wrong, but because it is ugly: ‘Nothing of ought, nothing of must, nothing of obligation’ (2: 231.32). Women ‘do something only because they love to’ (2: 232.1) not because of moral principles. In the latter, Kant declares that men should not count on a woman’s conception of her duty to ensure her fidelity, but rather keep her loyal through love and honour (20: 77.1–5). According to these claims, women cannot but act on their inclinations or feelings and they can never act for the sake of morality. If women were truly incapable of acting from duty, they would indeed not be moral agents in Kant’s sense, and not possess the same rational capacities as men.

However, whilst Kant greatly deprecates women in his Observations and Reflections, we must keep in mind that these works are pre-Critical. Even without entering the fraught debate about when exactly Kant introduced a conception of action from respect for the moral law into his ethics,Footnote ²⁹ we can say that at the time of the Observations and the Reflections Kant did not yet envisage a moral agent who can act from reason alone. Kant might simply have thought that both men and women act from different emotions: men from a sense of honour, women from emotions such as sympathy, jealousy and love. Whilst this is still objectionable, it does not warrant the claim that women are not moral agents for Kant.Footnote ³⁰ The critical Kant, by contrast, admits that women like to debate the potential moral worth of actions and considers this an expression of their genuine concern for morality (Critique of Practical Reason, 5: 153.13–154.16). This is of course still highly belittling and does not show that Kant thinks that women can do more than talk about morality. Ultimately, what Kant thinks about the agency of women after he introduced autonomy and respect for the moral law into his philosophy might be unanswerable. In his major critical writings on moral philosophy, he focuses on the source and supreme principle of morality (Groundwork and second Critique) as well as on the application of this principle to more or less concrete cases (Metaphysics of Morals). Many important questions, such as who counts as a moral agent, are left open.

It is not clear that Kant does really think that women lack reason, autonomy or agency and thus, in what follows, I will focus on legal inequality, since it is very clear that Kant assumes that there are significant legal inequalities between men and women.

5. Kant on Different-Sex Marriage

According to Kant, the marriage contract requires equality between partners (section 1), and inequality can disqualify certain unions from rightful marriage (section 3). Thus, given the stark de facto legal inequalities between men and women (section 4), Kant cannot, according to his own account, approve of different-sex marriage.Footnote ³¹

In fact, legal inequality is such a big obstacle to different-sex marriage on Kant’s account that it is not even clear that women have the legal standing to enter into a marriage contract at all.Footnote ³² After all, one of the reasons why marriage is good for women, Kant believes, is that women acquire a curator who can take care of their legal affairs for them (see 7: 209.5 and section 4 above). Presumably, women do have such a curator prior to marriage as well, normally their fathers. However, Kant never claims that a marriage contract is between a man and another man who is the legal curator of the bride. Moreover, there could hardly be anything less indicative of one’s respect for one’s future wife’s humanity than to enter into a contract with a completely different person about the use of her sexual organs. We should therefore assume that, according to Kant, women can enter contracts with men, but that their legal status makes them the decisively weaker party.

Clearly, according to what Kant himself says about men and women, they are not equals in any standard sense of the term. Importantly, they are also not equals according to what Kant correctly says about the status of women at the time, namely, that women are de facto deprived of full participation in society. Thus we cannot simply solve the tension between Kant’s conception of marriage as between equals and gender inequalities by concluding that he should just drop his sexist prejudices and stereotypes. Clearly, he should. However, as a matter of fact, women at the time lacked important rights and were in a very real sense not equal to men. This matter of fact inequality to which Kant is sensitive is central for my argument. It shows that it is not the case that my argument proceeds via a particularly charitable reading of the implications of his theory for the morality of same-sex intercourse and a much less charitable take on his remarks on women. Some of Kant’s remarks pertaining to women’s lack of rights and of opportunities to participate in public life reflect inequalities that exist independently of Kant’s own sexist attitudes. We can therefore bracket his merely sexist remarks for the purpose of my argument, just as I suggest that we should not rely on Kant’s homophobic statements, given that they cannot be sustained in the context of his own theory. I suggest that, across the board, we abandon claims that do not fit with Kant’s theory, work out what his theory entails, and then apply the theory to the social reality as Kant correctly captured it in observing that women do not have the same rights as (some) men. This, of course, raises the question of what the upshot of Kant’s conception of marriage would be for a society where men and women do enjoy equal rights. I will take up this issue below. We first have to look at legal inequality in more detail.

Due to inequality before the law, women cannot acquire important aspects of full citizens’ personhood. The best example of this is the right to vote. If I, as a full citizen, have the right to vote and my partner does not, there is, so to speak, something that I own and that my partner cannot acquire. This is unlike other differences such as that I own a car and my partner does not. The car could simply become our joint property. In the case of rights that my partner cannot share, my personhood extends to fields that my partner cannot share.Footnote ³³ No matter in what sense men and women might be equals for Kant, for instance as rational agents, in the sense relevant to his conception of marriage they were not equals in Kant’s time.

Admittedly, it might be odd to think of the right to vote as something that can be owned, but as I explained earlier, property relations are Kant’s model for legally relevant interpersonal relations. In these terms, then, passive citizens can have equal access to active citizen’s bodies and property but not to their rights, and both can therefore not fully and reciprocally possess each other as persons. Whilst this is potentially a problem for all couples (different-sex and same-sex), it is easier for same-sex couples to satisfy the equality requirement, since in same-sex unions both partners are ‘of the same kind’ (‘Beautiful and Sublime’, 2: 228.34), to speak with Kant, or more likely to be able to share the same rights. It seems that, according to Kant’s conception, all or at least the vast majority of eighteenth-century women were not eligible marriage material for male full citizens, and viceversa.

However, this might still leave room for two kinds of different-sex marriage even on Kant’s account. First, women who have attained active citizenship, if this is possible, might become spouses of active male citizens and, second, passive male citizens might be able to marry passive female citizens. The first possibility hinges on whether women can attain a citizenship status equal to that of male full citizens. Many of the circumstances that, according to Kant, bar women from full civil participation are a product of non-ideal, unenlightened social circumstances. Kant even once claims that ‘anyone can work their way up from their passive [civil] condition to an active one’ (6: 315.19–22).Footnote ³⁴ It would then be a direction of progressive transformation of society to liberate women and others who are being denied full participation. The possibility of different-sex marriage on Kant’s framework would then be something to strive towards and the result of an accomplished enlightenment. We should bear in mind, however, that active citizenship might only be one hurdle among others. Even active male and female citizens might be unequal in the sense that, unless gender inequality of all kinds is radically eliminated, active citizenship might be much harder to attain, maintain and exercise for women than for men. This raises the question of how to understand the impact of forms of inequality other than legal inequalities in the sense that certain people are explicitly denied rights.

The second possibility also requires that we think more about the impact of other than strictly legal inequality. Passive male citizens still have the upper hand over passive female citizens in the sense that it is easier for them to ascend to active citizenship. In addition, there might be important gender differences even within the respective classes of citizenship: passive male citizens will be much more likely to have the economic upper hand, they will be more respected by society, their opinions will count for more, etc. Much of this of course also holds for a different-sex union between active citizens.

It seems then that, according to Kant’s conception, all or at least the vast majority of eighteenth-century women were not eligible marriage material for men, or at least for male full citizens, and viceversa. Has this now changed? Whilst the legal status of women today is very different from the late eighteenth century, there still obviously exist widespread economic and other gender-inequalities. These, whilst not a form of legal inequality in the strict sense, stifle women’s full participation in civil affairs and the exercise of their maturity.

I cannot here settle the question whether Kant’s conception of marriage would still rule out different-sex marriages today, as this would require a more in-depth discussion than can be afforded me. In any case, the decisive issue is whether equality as persons only requires the same legal rights, or also the same protection by the legal system and even the same opportunities to exercise legal rights. At Kant’s time even the first of these conditions did not obtain, whereas nowadays in many societies it does, but even these societies still often fall short of making legal systems work equally well for all and of affording the same opportunities to exercise rights, as these opportunities are frequently restricted by economic and social factors.

A further question for Kant himself would have been this. Even if different-sex marriage was inconsistent with right at Kant’s time, what would have been the alternative? Staying in a sexual state of nature would endanger the survival of the species or at least entail that the species could only be preserved by immoral means, outside of marriage. Alternatively, maybe the institution of marriage itself could have become a mechanism for establishing gender equality? This, however, would not work as long as we hold on to the idea that marriage already requires a form of equality. This is an idea we should hold on to, I believe. The equality requirement is the intuitive and plausible core of Kant’s conception of marriage. Different-sex marriage, something that many still see as of significant social importance, cannot be rightful as long as women are not full and equal members of society and it cannot be a relation between a master or curator and an immature or disadvantaged domestic servant. In addition, even if marriage established equality between the spouses, for instance by mandating that women are granted all the rights of their spouses, in the absence of other and more universal tools to establish equality before marriage, this would still leave unmarried women deprived of certain rights.

Here it seems to me that we would simply have to envision the possibility that Kant might have overcome the assumption that a couple is either married and enjoys mutually enforceable rights and protections, or they are not and no (or hardly any) protections obtain. In particular, on such an assumption, it would indeed be a problem if heterosexual intercourse, the main way to procreate, could not take place within the context of a rightful marriage.

The problematic assumption here is that it is only marriage as a contractual institution that can render sex morally permissible. Marriage is supposed to create legally enforceable protections of partners against domination. But we now know that marriage is not uniquely suited to achieve this. Civil partnerships also constitute an institutional framework for partnerships, and even ‘mere’ romantic couples have legally enforceable rights against each other, such as against rape, physical abuse and in some countries even against controlling behaviour.Footnote ³⁵ With respect to our own day, in any case, the question might not be so much whether different-sex couples are now equal enough to marry, but rather whether there now exist ample protections for people to engage in sexual intercourse without endangering their humanity and opening themselves up to domination. Shifting our attention to this question would also address the worry that it still seems illiberal if intercourse is morally permissible only in the context of a marriage, even one founded on equality between the partners.