261 12

POLL Incest: Immoral or Moral?

I was asked this question today by a theist. If there is no God why is safe sex between brother and sister immoral to an atheist? This guy was smart to add safe sex because it closed off my avenue to argue the health issue. So, I was thinking why is it immoral if it is consensual? I understand we find it gross but is that because of Christian influence?

View Results Add Comment
By paul1967
Please or register to see comments



It's hard for me to respond to the poll because it says 'Incest: immoral or moral', but then it limits it with one particular example- that actually does not define 'incest'. The most common form of incest worldwide occurs between girl children and their male parents characterizing a drastic imbalance of power that can not be explained or be limited by religion/s, and where invariably girl children suffer lasting damages.
As well, it's not a matter of 'morality', it's exploitation.

Maya405 Level 7 Nov 7, 2017

Thank you!

this question carefully specified that both were adults, consenting, and practicing safe sex. without any single one of these conditions, my answer would have been different

I agree, and I think everyone would agree that is obviously immoral. The word immoral doesn't do it justice, and I can't imagine a word that would adequately describe how horrible that crime is, and that's precisely why I phrased it the way I did. I would never have wasted your time or mine asking the question, is rapping your daughter moral or immoral? The question itself is utterly terrifying. The question, is about consensual sex between two consenting people who happen to be a bother and sister, is that immoral or moral?

paul1967, 'consensual sex between two consenting people who happen to be a bother and sister, is that immoral or moral?' in this case, again, it's not a question of morality to me, but of choice.

My thanks also..I learn so much here...

That's more of a rape than incestuous relationship. Of course it's a sexual activity between related people. So, as you said proper definition should be given for the word in this poll.

awesome answer tackling an element of the subject I had not considered.

Great answer Maya, I am starting to enjoy reading such good common sense.

I don't know if and when religion took hold of incest, but between adults it just is. We mostly don't do it because it's bad for the gene pool. Island people got away with it in time past because they had great genes. But even then, a group has to eventually go outside of an insulated group to keep from weakening the pool. I think any culture has a right to develop its own system of who has sex as long as children are protected and valued.

yes, @Maya405, & we do make our choices based on our moral codes, don't we?

you didn't read the question, which specifically was about SAFE (non-procreating) SEX between SIBLINGS. & that would be a matter of your personal choice, based on an ethical or moral code.

@VirginCotton Parents, no, period. Regarding an aunt or an uncle, there are cultures where this education is respected and revered, and also tightly bound by tradition and ceremony. Under those circumstances, in those cultures, I would not call it incest. Outside of those cultures it is incest, and even in those cultures, outside the formalities and traditions of that education it is still incest and taboo.

@VirginCotton I've checked the Merriam-Webster online dictionary and the Oxford Living English dictionary regarding the definition of the word taboo. Merriam-Webster doesn't mention religion at all in its primary definition, and the Oxford dictionary I searched said "social or religious" in each definition. The word comes from the Tongan word "tabu" which means set apart, forbidden and makes no mention of religion. I also looked up "incest" and it refers to definition by law, not religion although of course in some times and places the two are just about interchangeable. Anyway,I checked the definitions to be sure I understood the words I was using, and now can confidently stand by them: I do not believe I am leaning into religious dogma; my references are social and subjective to the particular society as I mentioned in my answer. I do not know what I can help you with; I do not understand your reference to new territory. Is it because people are taking this discussion far beyond the original, very specific question? For me, it is incest without question, but the morality/immorality of it I cannot decide; it is a matter of choice for the two individuals involved assuming they believe they are,treat each other as, equals.

@Maya405, consensus, or agreement if you will, is the choice here.

@madmac, you just missed reading &/or understanding the original post.

@Rugglesby, nothing was answered in this comment. every single element from the original post was twisted into something else entirely. the question was about consenting siblings having safe sex. Maya405 turned this into a rape scenery between father & daughter, thereby hijacking the post.

@walklightly true, I caught the comment and applied it to the heading, kinda missed the other bit. Reading in full, I guess it's not really immoral to me as an atheist, just icky.

yeah, @Rugglesby, that'll be about it smile009.gif

@VirginCotton A 7-year-old boy is prepubescent and even a 12-year-old girl should not be in any kind of sexual situation with him. An adult male having an affair with a first cousin depends on whether the cousin is at least at the age of consent, generally 15 or so in most states. If she's at the age of consent but below 18, it's still incest and I think he could still go to jail for it. If she's below the age of consent, I think that's the legal version of not through puberty yet, and not only is it incest but also pedophilia, and he WILL go to jail and probably be killed by the other inmates, hopefully by being sodomized until his rectum ruptures and poisons him with fecal bacteria. (Gee, can you guess who was a victim of incestuous pedophilia? At the age of 6, no less.)
If the man having the affair is the grown boy of the scenario with his 12-year-old aunt, he is no less culpable: being an adult means taking responsibility for your actions, even if you are emotionally tainted with a history of incest/rape.

Maya just about nailed it.

Well said, however the original question harks back to the Christian claim that only they have morality...

I agree it is a matter of exploitation. The action also has mental as well as physical consequences.


first of all, I know people who are the products of incestuous rape that have no deformities. I also knew a lot of people who come from parents not genetically related who have major disabilities, so that isn't an issue. Besides, off you're having safe sex.....

This is one area where we are taught that is gross. But since it happens, it's perfectly natural.

The fact is that morality isn't about what you think other consenting adults are doing. Morality is about conducting yourself with integrity, and not allowing your preferences to hurry other people. So incestuous rape is immoral. Incest between consenting adults is not. Just like any rape is immoral, but sex between consenting adults is not.

Cheri Level 4 Oct 28, 2017

My concern is the medical/genetic point of view. Incest can and does cause genetic concerns. Granted it may not cause it in every case, but the potential is always there. One scenerio poised above was separated at birth, found each other , fell in love, and etc,etc,etc. children in such a case could and probably would gave some genetic abberrations pop up. Genetic counciling and testing would be wise. The moral aspect? I don't see a problem there, but from a legal point of view, there is a problem. In mist states relatives closer than second cousins are forbidden from marriage because of the potential for genetic changes, often times harming th children. I have seen the genetic aberrations from close family marriages. Most suffer mental retardation and physical challenges. Living in the south I have seen dozens of families that had children that had major health problems from incestious relationships. Look at the Middle East. In mist underdeveloped countries many marry family members due to the fact that they seldom move more than a few miles from their homes. In Islamic countries they state that 25% of the population has mental illness due to having children with close family relations. It's not uncommon to seefirst cousins marry. Not just in Islamic countries but in many Asian countries and India. The birth defects in close familial marriages are well documented.


As I understand it, First generation incest causes no disorders; that myth has been dispelled with modern genetics. Recessive genes do get a larger chance of expression but those genes may be beneficial or not or simply not an issue (like hair color). However, this can happen even outside incest if you procreate with someone that has those same recessive geners

As I understand it, It's multi-generation incest that causes disorders as the genetic pool is thinned out to the point of causing heritable mutations.

Well put.

@TheMiddleWay ...probably what happened with Adam & Eve & Caine... imagine.


Lol... I'd rather not... shudder!

@TheMiddleWay According to this study there's a 42% chance of abnormailty in 50% relations, which is pretty high. I'd always thought it was less. I wonder what it is for the general population. [psychologytoday.com]


@girlwithsmiles I don't know! I must have the luckiest family in history. Lots and lots of child molestation going on, but few problems. Maybe my recent ancestors had amazing genes! 😊


"So, I was thinking why is it immoral if it is consensual? I understand we find it gross but is that because of Christian influence?"

Yes and no. Incest tends to be a universal taboo. Other species (though not all) have evolved a host of strategies to prevent incest (for fitness reasons). Even plants tend to possess anti-incest mechanisms.

I voted that incest was immoral because most incest does not occur between two consenting adults. With that said, I don't see incest as an immoral act when every precaution has been taken to prevent pregnancy (if between male and female) and STDs between two consenting relatives. However, I find sexual relationships between mother/daughter, mother/son, father/daughter, father/son a bit disconcerting. Young siblings may do it out of curiosity.

The one you are in the debate with assumes it requires a god to see the problems that can arise with incest. It doesn't. Humans have learned by forming and testing hypotheses, building on working models of the social world as they interacted with it, and consulted these models when making moral judgments (Turiel, 1983). If incest wipes out half your tribe, it doesn't take a god or religion to figure out that this behavior isn't in their tribes best interest. Just my two cents.

VictoriaNotes Level 8 Oct 13, 2017

I enjoyed reading your comment. It was well thought out and reasoned. I wish I had waited for this before I responded to my opponents point. I will save it for the next time because this morality position theist hold is a prevalent one. Thank you for taking the time to write it.

Paul, I really appreciate your feedback. Your question was thought-provoking.

Outstanding answer! thank you!


First "safe sex" doesn't necessarily eliminate the possibility of pregnancy.
Second in reality invest isn't often consensual. So any abusive or exploitive sexual relationship is morally repugnant.

JimG Level 7 Nov 8, 2017

What about 2 siblings that were adopted by different couples raised not know each other. Meet fell in love got married then found out they were siblings. Is that still wrong if why

CCcatlover, that's kind of a stretch, but I have heard at least anecdotally of that or similar situations occurring. It's impossible to judge anyone in that situation as immoral. If they decide to stay married and especially if they have children, it becomes wrong. It's been pointed out that perfectly normal children have resulted from incest, but the chance of deformities is greater and becomes more likely if incest occurs over succeeding generations. If allowed where should we draw the line? I mean if a brother and sister have children why can't their children and grandchildren?

@JimG There were a couple of documented cases over the last thirty years or so. One quite tragic as the couple had children (healthy) but were legally obliged to divorce.
Back to the OP, the question ruled out offspring as a consideration.


CONSENSUAL, SAFE sex is nobody's business but the the participants!

AnneWimsey Level 7 Dec 18, 2017

I'd still like to make sure they're of a legal age myself. Parents that allow this to happen underage seriously change the ability of the kids to have successful future relationships. Plus the instigator is often the elder and therefore it is still a control situation rather than loving. No/limited insight from children into the potential damage they are inflicting on their younger sibling.


As long as it's consensual on both sides and they're the same age and using protection I honestly can't think of any reason why not, other than "eww". But that's not exactly a concrete basis to form our mortality around.

Ariel Level 4 Nov 16, 2017

I honestly don't think I can be rational about my response because the "Ewwwwww" factor is just too high lol

Ha I get that. But hey, who's it hurting? I feel like things are only truly crimes if there exists a victim. That's not to say I wouldn't still judge personally of course.

Thank-you cuz all I could come up wIth Is ewwwwww!


It's a neutral area when sex is between two consenting adults. It is like asking if a woman who is of the age of consent decides she wants to sell sex and is not coerced nor is she engaging in survival sex work is she acting morally or immorally. It is neutral. I disagree with giving those two choices but I see your reasoning why.

I want to thank you for taking the time to read the entire post. So many answers I've gotten have been from people who clearly read the title but didn't read what I said about it. I'm guilty of that myself from time to time, so I'm not bashing anyone, but I just wanted to thank you


In theory, incest wouldn't be immoral. But the way our culture works, brothers and sisters, children and parents do not have sexual relations. For this reason, there is too much emotional baggage and damage potential. I would not condone a sibling relationship, because it is fraught with potential for serious problems.

If I met someone who told me they were INVOLVED in such a relationship, depending on the details, I wouldn't feel the need to end the friendship or lecture them. I could accept it in some circumstances, I think. But relationships are hard enough without adding cultural baggage and emotional damage.

CatByrd Level 4 Nov 9, 2017

If it is safe sex, as stated, and the two people are adults I see no problem. The issue of incest has been mostly due to religious restrictions and due to the fact that if children are born from the union of the two people certain genetic abnormalities are very possible. As long as there are no children from the union then who am I, and why would society, have anything to say about two people enjoying each other sexually. Interestingly, due to my upbringing, my emotions are telling me to take away what I have just written above, but my mind over rules and says that if two consenting adults choose to enjoy a sexual union without children, why not?

Yes, with every fiber of my being I wanted to reject it but logically I feel the same way.


Morality is subjective. The morality of theists comes from a book which, taken literally, says we are all products of incest. So much for the religious argument against.

antitheism Level 4 Oct 30, 2017

I believe that if both parties are consenting and their intention isn't to have children, it is moral. Like other commenters are mentioning, incest can lead to birth defects and gentic mutations that would lower the quality of life for the offspring. If contraceptives or other methods are used, I see no reason why two relatives couldn't have a prosperous relationship.

jadeb99 Level 3 Oct 20, 2017

A great answer, consenting adults are the two words that in my mind make the difference.
Falling in love is the most beautiful experience ever and if it is true love felt from the heart people should be able to grasp it and enjoy it without the disapproval of others


Perhaps mine is not going to be a popular opinion, but my moral compass is governed by the principle of doing no harm. If incest is consensual and they aren’t trying to reproduce, then it does not harm anyone and both consenting adults have a right to be happy.

You should ask said theist how Adam and Eve populated the earth. Or remind them of the daughters of Lot.

Sntrada Level 2 Dec 24, 2017

if it's between consenting adults, it's fine. just like all sex. I don't understand why the question still comes up or why people can still be arrested for having consensual sex.

basher Level 2 Nov 4, 2017

I agree. I find it unappealing myself but I also find gay sex unappealing but I don't judge anyone for it and I know if they're happy and it makes sense to them I'm all for it.

How about if its between consenting adults, and the younger adult was raised to believe that it was ok and that was his or her role in that relationship from childhood? Is it ok then?

@rafferty that wouldn't be between consenting adults. you answered your own question.

No I didnt. I was describing a particularly awful form of sex slavery, and the very opposite of free thought. Monstrous. Ive seen the results such criminality.

@rafferty grooming a child into adulthood to be your sex slave is not a consensual relationship. obviously.

@basher But I believe that without some sort of investigation into it, they would seem perfectly consenting.


I find this hard to vote for one way or the other. Incest may be an emotionally safe scenario if there's no power-play going on, as siblings know each other well and (if raised well) have healthy trust for each other. On the flip side, there is SUCH a stigma attached to it, their lives would be devastated if found out. Why risk it? So, I can't make a moral judgement, as I think that is a false dichotomy based on an outmoded value system. I think what I'm saying is that morals are a construct that can be good or bad.

(...see what I did there???) smile009.gif

Hominid Level 7 Nov 3, 2017

I have to tell you that I like the way your brain works and even better the way you express your thought verbally. I do disagree on this point. The fact that society stigmatizes incest doesn't impact the question of is it moral. The issue should read, is it moral to you? I personally think it's unquestionably moral and very unadvisable. When I say it's moral I'm not implying good I'm saying it's not bad and my assessment of what is moral or immoral is based on is it Bad? Or not bad. I don't use, is it Good or bad because something that is moral doesn't necessarily mean it's good or advisable.

Ill make the moral judgement. One person has gone ftom bathing and feeding and taking the other person to school, to fucking them, and its now a romantic relationship dynamic, controlled and defined by the "parent". There is no way for this not to be abuse.

Also, people are going "oh brother and sister is ok.." Really? Where's this? Alexandria in the 1st Century? (Ptolemies like Eurgetes "potbelly" or Chickpea were reviled and openly mocked as inbred degenerates, which was true) or Caligula's Brothel palace? He would make everyone swear loyalty oaths on his sisters names to put that they were fucking in people's faces, specifically to offend thier senses of morality, and it got him assassinated. cassius Caerea cited "Degeneracy" as a valid reason, and proof he was a lunatic.


Because no age parameters or relationships were given, I am going with immoral under the assumption that there is a significant age gap, disparate levels of education/power/wealth, or other inequalities that would put one party at a disadvantage. For example, a girl and her Father vs two 35 year old first cousins are vastly different scenarios.

DispatchKara Level 3 Oct 30, 2017

There were no parameters given, so I will say immoral when it's father/daughter or uncle/niece. (I've read older male on younger female is most common form of incest.) The power within the authority figure in such cases bring me to the immoral side of the argument. I would also say immoral if it's mother/son or aunt/nephew. I believe even well into adulthood there is always that authority figure issue with parents and aunts/uncles. Now, sister/brother or first cousins are relationships that should be judged on a per-case basis. Is one more dominant than the other? It would, of necessity, have to be an egalitarian relationship for me to go to the moral side. I've enjoyed reading everyone's comment on this topic.


I don't know if I would say that it was moral as much as I don't think its inherently immoral. Of course that statement has to be qualified. I think if both parties are consenting adults, and that assumes that there is no coercion, then I can see anything objectively wrong with it.

Davetheatheist Level 2 Oct 28, 2017

There should be a third option..like depends. Because if people were separated for years through adoption or father was a sperm donor..if they somehow found one another and started a relationship..only to find out later on they were related..how can we as a society deny them when they were not aware of the relation? If two men and two woman either twins or brothers and sisters close in age start fool around..its taboo and morally wrong but if god does not exist like most of us believe..how is anything immoral? Who makes these rules? As long as you are not causing harm to others who cares what someone does. So I guess incest is fine in my book within reason..appropriate ages..and situations..and 100% safe sex so children can not be spawned from such actions.

If its first generation brother sister the deformity rate is still relatively low. It when generations keep doing it that causes health risks

Also, parent and child relations is a lot more likely to cause problems than between siblings.


Your family is a place of safety where all emotions can be explored but the boundary to sex shouldn't. Physically, genetic mutations make it rightly taboo and emotionally it should be taboo as you can go out into the world and literally fuck up your life, but you shouldn't fuck up your family and place of refuge.

Hugene2002 Level 7 Oct 17, 2017

I am a little disappointed in the answers. They all seem to be addressing child molesting or genetic dangers. The question was phrased in a way to make it if two grown, consenting relatives want to have sex, is that immoral. Not have children, not prey on children. The hypothetical question is about sex between two consenting, related adults.

Benmonk Level 6 Dec 28, 2017

Thank you!

As long as those conditions are met, I would vote 'moral' in that individual case. But that doesn't let incest off the hook in general.

Take murder, rape (of an adult) and child sexual abuse. Each one considered more morally outrageous than the last, in modern Western society. While rape and child sexual abuse at least leave the victims with lives to rebuild, we literally treat them as worse than murder. Why?

I believe it's a deterrent. We big these things up into being the most atrocious of atrocities precisely because there are people out there right now who are facing the temptation to do these things, and we need them to know that doing them makes them bad, bad, bad, BAD people.

Sadly (for those rare cases of consenting incestuous adults with no history of grooming) incest needs to remain immoral and illegal precisely to stop these behaviours. You really can't have a question on the morality of incest without raising the genetic or child grooming issues.

No sorry, @BenMonk he doesn't actually state that the parties are adults, hence much of the conversation is clarifying this. But given that you assume they are adult I assume you are not against it? Me neither if that's the case, their choice.


I can't say moral or immoral because those are social judgments based largely on social norms, but also on facts, such as inbreeding. But the truth is that pederaste was common and accepted for generations in Europe, royalty and aristocracies have in-bred publicly and even today, supposedly "moral" religious practices (not just LDS cults) marry off their children at young ages even to close relatives. I'm not sure how society has come to look down on what we call incest, but I'm sure that had a lot to do with the advent of rights-recall that even in early America, women and children were chattel and could be beaten by the male owner... until society started changing the narratives and fighting not only for women's rights, but also for the rights of children to not be abused... and our social definitions of child abuse have also changed consistently and incessantly for eternity.
As a product of a western society upbringing, I still have thoughts about incest being abuse, but, a better question is to ask the theist to justify all the incest, pederaste, and the forcing of victims to marry the rapist...Which is more "immoral?"

CrankyAntie Level 4 Oct 30, 2017

I cannot vote yes or no because I have to object to the use of the terms "moral" and "immoral," since both are ground in religious presumptions of a sort of natural law. To say something must be avoided BECAUSE it is wrong is, to a secular thinker, ass-backward. We are, rather, taught certain things are immoral in order to scare us away from doing things that our society or culture believes would be destructive in some way. So...the question should be "Do we think incest is harmful or not?" To me, the answer cannot be absolute, because there are exceptions, but in general I think it could be harmful, not just because of potential for genetically compromised offspring, but also because it might mess with the other social aspects of family relations, either with the specific persons committing incest or with their relations with other family members, or both. I do believe, though, like any self-respecting situational ethicist, that there are valid exceptions sometimes. Others on this thread have already pointed to some, and historically our definitions/parameters for which relatives involved would constitute incest or not. What about identical gay twin brothers who felt closer to each other than to anyone else? Personally, I think the main difficilty in that situation would be how the two handle reactions from other family members who would be upset with them.


As atheists, we understand that society at large - the community as it were - dictate morality. Individuals do not. And as a society, we've deemed it "wrong"... and that is not arbitrary. In fact it's actually illegal in most states.

MartinDeBourge Level 2 Oct 13, 2017

I like the way you put that. I'm preparing my response, now so I may incorporate what you said in my response. I was heading in that direction, but you worded it better.


Society has certain rules be you a religious or not. There are many religions, I'm sure that would welcome the practice of incest. I like to consider myself a liberal, live and let live, blah blah, but I also work in family law. The cases I have seen in 35 years with incest somehow end up to be more one-sided. Again, with the male convincing the female the it's ok. In fact look at all these people on this website that agree with me. I'm sorry but I disagree. If the only person you can find to form a loving sexual relationship with is in your immediate family, you might want to seek counseling.

Movdsouth Level 2 Mar 4, 2018

I actually don't see it as a huge deal if cousins or distant cousins decide on having some sort of relationship or even children. The genetics would be way more diverse and you wouldn't be raised in the same household so it's not the same as siblings.

Now siblings is immoral for many reasons. Your children would face repercussions of not having enough diversity in their genetics one way or another. If the siblings decided on just a sexual relationship then there is A LOT of emotional problems that could and will occur if it happened and shame since it's a very taboo thing and could ruin your relationship with them as a whole.

LadyStardust96 Level 5 Nov 11, 2017

Well...if you are looking at it from the biological perspective of reproduction, there is that risk of passing on genetically inherited flaws and afflictions (weak chins, poor vision, disabilities) so it may not be wise. On the other hand, if you don't have any genetic markers for health concerns you would strengthen your bloodline and could lead to a better, faster, stronger (depending on strengths) specimen. Kinda hard to get past the 'eww ick' factor. When you are your own aunt, things get weird. But you probably will get something better than socks and an autoharp cd for your birthday. I don't think that immoral or moral are really the best choices because morality generally is passed down through religious dogma. Better to say gross or not gross. Not easy to get out of the gross camp. If it were a social norm with which I had grown up I would likely feel differently.

Gatekeeper63 Level 5 Oct 31, 2017

But from a biological perspective there is the biggest problem - we share 25% of the same genes as our siblings which is likely to cause genetic abnormalities to the offspring. But what you may have missed in the question were the words "safe sex".

Write Comment
Agnostic does not evaluate or guarantee the accuracy of any content read full disclaimer
  • Agnostic.com is a non-profit community for atheists, agnostics, humanists, freethinkers, skeptics and others happy without religion!