Arguing Equality Chapter 6: Gay Marriage is Slippery Slope?

This is a nine-part installment designed to help everyone understand marriage equality.  For some, it will be an education, for others, it will be helpful when discussing the subject.  I have included links to each chapter at the end, as well as information about the author.



Gay marriage would be the “downfall of Western Civilization!!!” We’ve all heard this preposterous claim. Click here to explore it.


Marriage has traditionally been defined as a union between: (1) two persons; (2) of different sexes; (3) that are over the age of consent; (4) and are not related. If we alter or ignore these restrictions and permit same-sex marriage, do we not risk opening the floodgates to the sanctioning of all types of familial arrangements? If society allows gay marriage, by what rationale could it stop polygamous marriages, pederastic marriages, or incestuous marriages?

This is called a “slippery slope” argument — in the words of William Eskridge, “Once you start going down the slope, you tend to slip to the bottom.”

Hadley Arkes, professor of political science, makes the case this way:

The traditional understanding of marriage is grounded in the “natural teleology of the body” — in the inescapable fact that only a man and a woman, and only two people, not three, can generate a child. Once marriage is detached from that natural teleology of the body, what ground of principle would thereafter confine marriage to two people rather than some larger grouping? That is, on what ground of principle would the law reject the claim of a gay couple that their love is not confined to a coupling of two, but that they are woven into a larger ensemble with yet another person or two? … [O]nce the arrangement is opened simply to “consenting adults,” on what ground would we object to the mature couplings of aunts and nephews, or even fathers and daughters…. All kinds of questions, once placed in a merciful repose, may reasonably be opened again. They become live issues once we are willing to ponder that simple question. Why should marriage be confined, after all, to couples, and to pairs drawn from different sexes?

A sarcastic response. Why stop at polygamy? Lets keep going and going…

A) Slipping To Absurdity

By taking this argument to its absurd albeit “logical” conclusion, one can see how silly it truly is. Look closely at the claim being made, that any alteration in “traditional” or “natural” restrictions on marriage will lead to the deterioration of all other marital restrictions. But if this were true, why stop at incestuous or polygamous marriages? If we are truly worried about these marital variations, why not necrophilic ones as well? What about bestiality, or even marrying an inanimate object if an individual claims to be in love with one and there are truly no restrictions on the form or function of marriage?

The very notion is manifestly ridiculous. Gay marriage is a legal and moral issue distinct from these others, and it as best disingenuous to argue that its legalization will force the government to recognize the sanctity of a human bond with an animal or a dead person. And will the state have to sanction polygamous, incestuous or child marriages. To intimate otherwise, Andrew Sullivan wisely points out, “is not an argument, it’s a panic.”

B) Slipping The Other Way

It would be wise also to keep in mind that slopes can slip in more than one direction, and can be used to support, rather than undermine, the case for same-sex marriage. For instance, if the state is permitted to cite “traditional restrictions” and ban gays and lesbians from marrying, what would prevent it from also banning other categories of people “traditionally” denied the right to marry? Not so long ago, people with mental disabilities and sexually transmitted diseases were “historically” denied access to the marital institution. If gay men and women are not permitted to marry on grounds of tradition, what could stop the state from denying these other groups the right to marry on grounds of tradition as well?

Going one step further, anti-miscegenation laws, on the books of some states from as early as 1691, are as “traditional” as any law in this country. Also part of our country’s tradition is a legal conception of marriage whereby a woman is considered the “property” of her husband. If the state opts to ban gay marriages because it wants to define marriage traditionally, as a matter of intellectual consistency do we not risk the return of these other antiquated, albeit “traditional,” definitions of marriage as well?

If you haven’t figured it out by now, slippery slopes don’t usually have much logical sway. Usually, they can be outright dismissed on their face.

C) Slippery Slopes in General

Within Harvard University’s Speech and Parliamentary Debate Society, students are taught “The Five Deadly Opps,” five arguments which can be used in virtually any situation to oppose virtually any proposal for change. They are:

  1. It costs too much (not necessarily economic costs).
  2. It does not solve the underlying problem.
  3. It targets the wrong people.
  4. It applies a short term solution to a long term problem (or vice versa).
  5. Where do we draw the line?

The problem with all of these “opps” is that, while useful for purposes of debate, in their extreme form they are intellectually dishonest and imply that no social reforms should ever be undertaken. The simple truth is that gay marriage will not lead to incestuous marriage. Countries such as Denmark, Sweden, Canada and the Netherlands, and most recently Massachusetts have all legalized same-sex unions without legalizing polygamous or incestuous ones.

As I shall explore in the next section, marriage has evolved numerous times over the centuries. Women are increasingly seen as equal “partners” in a marital relationship. Persons of different religions and races are now permitted to wed. Mentally handicapped people and people with sexually transmitted diseases are also now extended that right. Indeed, the only consistent, traditional aspect of marriage is that it has constantly changed to reflect society’s understanding of the equality of individuals, and today we are coming to recognize that the choice of a marriage partner should belong to the individual, not the state.

In sum, if one believes in this line of argument, when talking with them you might not even need to address the issue of polygamy. Ppolygamous marriages should perhaps be legalized, and perhaps they should not. That is an issue which our legislators may or may not take up, and is an issue different than, and should be treated as distinct from, gay marriage. Marriage has evolved for the better many times over the years, and will likely evolve even further in years to come – each change, however, has been and must continue to be judiciously analyzed and judged on its own merits. It is disingenuous, and callous, to treat any potential change as part of some seamless process of an alleged disintegration of an institution.

The conservative view. Attacking polygamy and incest to promote gay marital monogamy.

D) Concept of Choice

Finally, in addition to the aforementioned reasons, a distinction between gay marriages and polygamous and incestuous marriages can be made based on the concept of “choice.” Andrew Sullivan makes the case this way:

Do homosexuals actually exist? I think so, and today even the Vatican accepts that some people are constitutively attracted only to members of the same sex. By contrast, no serious person claims there are people constitutively attracted only to relatives, or only to groups rather than individuals. Anyone who can love two women can also love one of them. People who insist on marrying their mother or several lovers want an additional (and weird) marital option. Homosexuals currently have no marital option at all. A demand for polygamous or incestuous marriage is thus frivolous in a way that the demand for gay marriage is not.

via Gay Marriage is Slippery Slope?.


Seth Persily is a member of the Georgia Bar and a cum laude graduate of Harvard Law School. While at Harvard, Mr. Persily served as Publisher of the Harvard Law Record and co-President of the Lambda Law Association. Mr. Persily obtained his undergraduate degree from Duke University, where he served as President of the Duke Gay, Bisexual & Lesbian Association. He graduated Phi Beta Kappa, with a B.A. in Religion and a minor in Gay & Lesbian Studies.

Mr. Persily worked at the Atlanta law firm of Sutherland, Asbill & Brennan before opening his own practice, Persily & Associates, which concentrates on employment discrimination and real estate law. He serves on the Board of Directors for Georgia Equality as well as YouthPride.


  1. I loved a counter to the “slippery slope” argument, from a (Reformed) Jewish Rabbi on a British radio discussion. Her response was that she prefers to think of the slope as a hill to be climbed.


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