Biological Sex Is Binary

By your same logic, you would have to say that temperature is "binary," since "hot" and "cold" are the only two options and all other temperatures are on the spectrum. In fact, everything that is not binary would be binary by that reasoning. The term "binary" indicates two discreet options. If something exists on a spectrum, it is, by definition, not binary.

(opinion coming) I also wouldn't say that biological sex exists on a spectrum. For the most part, it is binary. The small percentage of cases are exceptions to the rule, but the rule (sex is binary) is still useful. This is like saying that a light switch can be either in the "on" or "off" position, but it might get stuck in the middle sometimes. It is still reasonable to consider the switch to have two positions despite this anomaly.

All of this comes down to the following: a good argument must have accurate premises. Otherwise, no matter how good your logic is, your conclusion will be bogus.

"Garbage in, garbage out."

In this case, the logic is bad, too, but the big problem is the inaccurate premise. False dilemma.

kylee, I think you correctly express the observable fact of distinct, sex-based states (organs) for humans, and that reference to a spectrum muddies your point. The presence of both sex organs is the rarity, and you are also correct that there is no third organ.

Your argument is sound, but not valid:
P1: Biological sex is binary if there are only two sets of sexual organs.
P2: Humans have only two possible sets of sexual organs.
C: Biological sex is binary.

The logic is correct.

The first premise depends on the definition of "biological sex." If it is based on organs and chromosomes, then it is mostly true. (There are rare occurrences of hermaphrodites, XXX, and XXY chromosomes.) By that definition, biological sex is binary.

However, if it's based on hormones, it is not binary. Levels of estrogen and testosterone vary widely in men and women. By that definition, biological sex is not binary.

Hormone levels affect how a person meshes with society much more than organs do.

Your question implies a scientifically incorrect binary distinction. This argument is often used for the morally dubious purpose of criticizing people whose sexual biology or behavior differ from society's norms.

https://www.mountsinai.org/health-library/diseases-conditions/intersex

The common term for your fallacy is "false dilemma."

Based on your premise, can you actually claim homosexual intercourse, or even heterosexual mouth, anal and digital stimulation to be non-biological? They certainly are not reproductive, but that doesn't make them non-biological. Is homosexual interaction binary by your definition?
There are just too many loose ends (haha!) going on here. False Premise, and it is misleading because without the reproductive angle it formulates upon an either/or fallacy.

As Dr. Bo explains:

Affirming a Disjunct

(also known as: the fallacy of the alternative disjunct, false exclusionary disjunct, affirming one disjunct, the fallacy of the alternative syllogism, asserting an alternative, improper disjunctive syllogism, fallacy of the disjunctive syllogism)

New Terminology:

Disjunction: A proposition of the "either/or" form, which is true if one or both of its propositional components is true; otherwise, it is false.
Disjunct: One of the propositional components of a disjunction.
Description: Making the false assumption that when presented with an either/or possibility, that if one of the options is true that the other one must be false. This is when the “or” is not explicitly defined as being exclusive.

This fallacy is similar to the unwarranted contrast fallacy.

Logical Forms:

P or Q.
P.
Therefore, not Q.

P or Q.
Q.
Therefore, not P.

Yes, all responses are correct (so far) on this simple proposition not matching evidence. "There are several variant disorders which include Tetrasomy X, Pentasomy X, 49, XXXX, 48, XXXY, 48, XXYY, and 49, XXXXY." So can this be binary? It would seem that the presumption of Binary doesn't accommodate these instances. Or this, " Mayer-Rokitansky-Küster-Hauser syndrome [a female?], meaning they don't have a vagina." How would you call this person's sex? So, the argument is not a fallacy if evidence is ignored. Sex is binary if these instances are ignored: no sex organs or hormones contrary to sex organs, and those who have genetic markers contrary (or complimentary) to their sexual organs. Defining terms is essential on logical and scientific analysis.

Addendum to my previous entry: "One 37-year-old British man (who goes by "Rob") was shocked when doctors told him he has fully-functional female reproductive organs. While Rob has normal male genitals, he also has a uterus, cervix, ovaries and Fallopian tubes. This is typical of a condition known as persistent Müllerian duct syndrome. "

I think you would have to rephrase the premise to binary "Reproductive Sex" for it to be valid because "Biological Sex" is too ambiguous if we consider the accessory organ systems that can be used in human sexual relationship.

Certainly the mouth and anus are parts of the Digestive Organ system, but throughout human history have played an important function in human sexuality and pleasure. Hence, they are biological, but not Reproductive. So, now we don't just have binary male and female Organ Systems that are unique to each sex (male and female genitalia) but also two shared similar Organ systems (mouth and anus) that are common in both sexes. So this seems to blow the premise of binary biological sex out the window. (Pun intended).