The Instigator
Con (against)
7 Points
The Contender
Pro (for)
0 Points

Is Incest Morally Wrong?

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Post Voting Period
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after 2 votes the winner is...
Voting Style: Open Point System: 7 Point
Started: 12/16/2012 Category: Philosophy
Updated: 5 years ago Status: Post Voting Period
Viewed: 7,622 times Debate No: 28308
Debate Rounds (3)
Comments (7)
Votes (2)




Debate request: It would be preferable if you have at least a BA (or its equivalent) in philosophy.

The Kind of Debate I Would Like to Have

First, I would really like to have a polite and civilized debate (i.e. no name-calling, incendiary language, etc.). I am not going to be treating this like a debate, but more like an intellectual conversation. I am genuinely curious to know if there are any compelling arguments against incest.

Second, I would prefer only to discuss secular and philosophical arguments, i.e. no arguments that rely on religious premises (e.g. there is a God or the Bible is the word of God).

Third, I would prefer to only rely on simple language"for the sake of clarity. I am not looking to be impressed by your vocabulary. In addition, if you introduce a concept that you think is essential to your argument(s), please define it and give examples of it.

The Form of the Debate

I would like my opponent to lay out what he or she thinks are the most compelling arguments for the conclusion that incest (of the variety I define below) is immoral. I will then respond and say what I agree with or disagree with concerning these arguments. And, then we will continue the conversation in the following rounds.

A Word of Clarification

Before offering a rough working definition of incest, let me clarify that this debate should focus only on the one kind of relationship: A sexual relationship between two adults that is heterosexual, monogamous, and consensual"as well as void of any other unmentioned controversial properties. The reason for limiting the debate to only this instance of incest is that I am solely concerned with whether or not incest is in and of itself is immoral. In other words, I want to know if the property of being an instance of incest is an intrinsic wrong-making property, i.e. a property of an act that counts against it moral permissibility. By intrinsic, I mean a property that exists in each and every instance of incest, such that if an act were to lack this property, it would no longer be considered an act of incest. Thus, we should bracket off any other controversial properties of sexual relationships as they may draw attention away from the topic at hand. With this in mind, I have no interest in debating incestuous sexual abuse, rape, etc. Such relationship are clearly not consensual and thus a matter for another debate.


Incest is a sexual and/or romantic relationship between two people who are closely related biologically and/or psycho-socially (e.g. first cousins, brother and sister, father and daughter, mother and son, etc.). One weakness of previous definitions of incest is their concentration on consanguinity (i.e. the biological relatedness) of the people involved as a necessary condition for incest. However, I see no reason for thinking that a romantic/sexual relationship between a parent and an adopted child or between an adopted child and her sibling should not be considered incest. In other words, consanguinity is not necessary for incest. By claiming that two people are "psycho-socially" related, I mean that they understand each other to have a socially defined relationship, which normally manifests itself in certain ways. This is admittedly vague, but I take as a primary instance of this kind of relationship the relationship between two siblings that grow up together and where one of them is adopted.

If you are unsure that a relationship involving two psycho-socially related people should be considered to an incestuous relationship, consider which of the following cases you think is more clearly a case of incest: (1) Two siblings (one of whom is adopted) group up together in the same house for 21 years and then begin to have a romantic relationship or (2) Two biologically related siblings who were separated at birth and who do not meet until they are both 21, at which point they begin a romantic relationship. Intuitively, I cannot help but find the first case to be a more obvious case of incest.


What is the purpose of genes? Of sex? OF DNA? VARIATION! And believe me... You're morally doing your species no favours by having a kid with a partner who is practically identical in all but every small portion of DNA. This is not how the human race got to be so dominant. We got here, and plan on staying here, by being the most VARIED species on the Earth! This is why we have countries and cultures in the first place.

Incest isn't inherently 'disgusting' or 'revolting' in the scenarios you stated. It is, however, morally wrong to think that truly your duty as a brother would be to guard the sister from bad husbands and dirty guys out there oh wait... YOU ARE THAT GUY! LOL! A sister's purpose to a brother is to advise him on the best option of women and perhaps whisper "she's not he one for you... Take my advice" but oh wait SHE IS NOW VERY BIASED! What of a father and daughter?... Even if both are over 18... Is this really what a father should do for his daughter? Isn't a father's purpose to stop dirty buggers form getting his girl and only the finest young man out there to do so? YES! BURN HIM IN HELL WHAT A DIRTY FATHER!!!!!!!!!! And a mother and a son is just plain dirty. Like seriously, she's with your dad and you're having her cheat with you, well I mean that's not morally correct in my book.

The only true morality I can see is if they just are the equivalent of friends with benefits. But even then isn't the point of FAMILY to have PLATONIC love (apart from the parent pairs)?!
Debate Round No. 1


First, thank you to RationalMadman (hereafter: RM) for agreeing to participate in this conversation.

Let us recall that I asked if incest possesses some intrinsic wrong-making property. I think that RM has not fully appreciated this part of my interest in incest and the importance of such a property will become clear in my responses.

1. Genes and teleology

The first objection seems to have to do with reproduction and its (supposed) purpose. First, this is not an objection to incest as such, but to inbreeding. While all instances of inbreeding are instances of incest, not all instances of incest are instances of inbreeding. Thus, this is not an objection to incest.

Second, I'm no biologist, but I'm pretty sure that the first humans had to mate with individuals that were practically identical with them and that turned out all right. In fact, it was necessary for us to get where we, as a species, are today.

Third, this ignores the fact that I've included family that is not biologically related (e.g. adopted children/sibling) as being capable of incest. If two sibling (one of whom was adopted) procreate, then this objection does not apply. Remember, I'm looking for an intrinsic wrong-making feature and that means it would have to apply in cases of both biological and non-biological incest.

Moreover, incestuous couples can have non-procreative sex (oral or anal), they could use contraception, they could get vasectomies and hysterectomies, etc. Furthermore, this objection would not apply to couples where one partner is sterile or postmenopausal.

Four, RM faces a line-drawing problem. What is the maximum amount of DNA that a couple can have in common before their relationship is immoral? For example, siblings have more DNA in common than an uncle and a niece (1/2 vs 1/4) and the latter have more DNA in common than 1st cousins (1/4 vs 1/8) and 1st cousins have more DNA in common than 1st cousins once removed (1/8 vs 1/16) and 1st cousins once removed have more DNA in common than second cousins (1/16 vs. 1/32) and so on [1]. Where must one draw the line of moral permissibility and why there instead of some other place?

Five, how exactly does one determine the purpose of a thing, a process, or an action? Can things have multiple purposes? Who or what determines these purposes and is it morally binding?

2. The purpose and duty of family members.

The second set of objections is why I requested someone with a degree in philosophy. This section is very sloppy and includes unnecessary capitalizations and exclamation points (no offense, RM). Using either of these does not make your argument any sounder or more convincing. I'm writing this not to be rude, but to ask that you try to write a bit clearer and without unnecessary flourishes. Remember, someone else (i.e. me) has to read this and think about it. The clearer you are, the more likely it is that I will not misinterpret what you've written.

This set of objections seems to be more about the morality of manipulating a person you have romantic feelings for. So, for example, RM mentions the brother and sister who do not help their respective siblings with finding a proper boyfriend or girlfriend, but instead give them biased opinions. Such manipulations are not in any way intrinsic to incest.

First, consider a male and female, who are best friends. The male has a crush on the female and gives her bad advice on boys in hopes of keeping her for himself. This, and other kinds of manipulation are wrong not because they are a form of incest, but because, like I said, they are forms of manipulation. Manipulation as such is wrong because it fails to treat people as ends in themselves; it fails to respect their autonomy.

Second, imagine the case of biological siblings separated at birth. They meet and fall in love without ever knowing they are related. There is no way of either of them manipulating the other in the way that RM has objected to. This also applies to a biological relationship between fathers and daughters and mothers and son. What if the children grew up apart from their biological parents? What if the children were given up for adoption and later falls in love with their biological parents? The kind of manipulation that RM raises in the second objection does not seem possible here. Again, RM is failing to pay attention to the intrinsic wrong-making property that I said I was looking for.

There's more I could say, but I'll leave it at that for now. I look forward to RM's response.


[1] Alan H. Bittles, "Genetic Aspects of Inbreeding and Incest," in Inbreeding, Incest, and the Incest Taboo, ed. Arthur P. Wolf and William H. Durham (Stanford, CA: Stanford University Press, 2004), 39.


At the end of the day I don't care about anything you just said.

If you actually have sex with your mother, sister, brother, cousin (adopted or not) you have failed to accept the emotional bond of family being platonic and closer than physical at its very core.

The only case where the human duty for variation come sinto context is that of siblings, separated at birth who fall in love unwittingly and suddenly realise... Sorry for those people but they shouldn't f*ck it's not the way.

This isn't even a debate, it's your opinion vs mine.

Peace be upon you, unless you are not peaceful. xoxo
Debate Round No. 2


In all due respect, this has not been just an exchange of opinions. You gave arguments for the conclusion that incest is morally wrong and then I provided reasons why those arguments were insufficient. While reason may determine my opinion, my opinion does not determine reason and what counts as reasonable arguments.

You wrote that if a person engages in incest then he or she has "failed to accept the emotional bond of family being platonic and closer than physical at its very core." I"m not sure what you mean by this, but I am sure that this is not a moral argument. You need another premise, namely: it is morally wrong to fail to accept the emotional bond of family being platonic . . .

Why do you draw the DNA variation line at siblings? Why not an uncle and a niece? What"s so morally salient about 50% shared DNA vs 25% shared DNA? And, of course, any argument concerning procreation does not address most instances of incestuous sex. Why? Because most instances of sex"incestuous or not"do not result in procreation.

I really wish you wouldn"t have accepted this debate if you were/are not willing to seriously engage in a debate about this topic.

If you do not continue with this debate, I will take that as a sign that you are forfeiting the debate. This is obviously fine, I just want to make sure I don"t waste any more of my time if you are not going to make an effort.

Reason be upon you, unless you are not reasonable.


I was requested to do the following; to say why " it is morally wrong to fail to accept the emotional bond of family being platonic." The reason it is morally wrong to fail to accept this is that to fail to accept the truth of family is to deny the people who you owe your upbrigning and a large portion of your perosnality and success in life to and thi is dirty tactics to betray them (if you cheat with your mom on your dad) dirty dirty dirty filthy icky disgusting I mean isn't that why we don't like rape, torture and murder?... BECAUSE THEY ARE DISGUSTINGLY DIRTY WAYS OF LIVING LIFE! I am a moral nihilist and the only source for morality I can draw on is the emotions of humans since no objective source of morality is unfalsifiable.

I was also requested to justify the following: Why do you draw the DNA variation line at siblings? Why not an uncle and a niece? What"s so morally salient about 50% shared DNA vs 25% shared DNA? And, of course, any argument concerning procreation does not address most instances of incestuous sex. Why? Because most instances of sex"incestuous or not"do not result in procreation.

I'll answer them one by one.

Why do you draw the DNA variation line at siblings? I didn't, I said 'cousin' in round two.

Why not an uncle and a niece? I never denied this, I just thought that an intelligible opponent wouldn't require his opponent to label each and every possible family member.

What"s so morally salient[Most noticeable or important] about 50% shared DNA vs 25% shared DNA? Double the similarity and by the way all humans have 99% shared DNA so your argument is really quite irrelevant.;

And, of course, any argument concerning procreation does not address most instances of incestuous sex. Well Christians say sex for recreation and not procreation is spilling the seed, so I don't see how you can morally justify promiscuous sex unless you can objectively falsify Christian god so really that was irrelevant to this debate.


Thank you and good night.
Debate Round No. 3
7 comments have been posted on this debate. Showing 1 through 7 records.
Posted by iamnotwhoiam 5 years ago
The first humans did not have to mate with individuals that were practically identical with them. Con might be taking a biblical view of the origins of humanity, which is contrary to fact. The population was never below 10,000 individuals in the last 1m years. Note that humans appeared approx. 220,000 years ago.

To the voting. Pro failed to give a serious argument that incest is wrong. "dirty dirty filthy icky disgusting" does not count as a serious argument. That family should be a platonic bond was promising, but he didn't follow through on it.

Unfortunate for Con that Rational Madman accepted his debate.
Posted by Pangloss 5 years ago
Posted by Pangloss 5 years ago
Posted by RationalMadman 5 years ago
Wanna know what?... Just listen to the song.
Posted by Pangloss 5 years ago
I apologize, I meant 50% of the same genes, not DNA. If this is not correct, then I suggest you read the article from which I got this information. As I said, I'm no biologist.

Also, "Christians say" is an incredible naive thing to say. Do you know every Christian? I can name plenty of Christians that think non-procreative sex is permissible. Also, the Catholic Church accepts sex between a married couple if one or more of the partners is infertile. But of course I asked that we leave religion out of the debate. You failed to do so when you got desperate for a response. Finally, the "Christian God" (whatever that means) most probably does not exist.

You should not be doing any more debates if you are not going to take them seriously. You are clearly a child, I'd guess you're under 20-years-old. And if you're not, then there's a bigger problem for you. Please grow up and stop wasting busy people's time.
Posted by miketheman1200 5 years ago
You poor soul, RationalMadman accepted your debate...
Posted by 16kadams 5 years ago
Pangloss!!! Last time I saw was when... Never you left before I came. But I read your SSM debate.
2 votes have been placed for this debate. Showing 1 through 2 records.
Vote Placed by Bodhivaka 5 years ago
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Total points awarded:40 
Reasons for voting decision: I believe Con presented a strong philosophical case demonstrating that incest is not inherently unethical. Pro's claim that incest is immoral simply because it is "icky" is rather unwarranted. Con also gets S&G points due to Pro's excessive and unnecessary use of capitalization/punctuation.
Vote Placed by iamnotwhoiam 5 years ago
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Total points awarded:30