One of the principal types of arguments against LGBTQ+ rights is the appeal to biology. Specifically, these arguments say that humans are divided into two biological sexes and the sexes are inherently different in ways we can understand scientifically, gender corresponds exactly to biological sex, humans evolved to engage in monogamous heterosexual relationships, and so on; furthermore, these arguments claim that humans should behave in a way that is biologically natural, and deviations from the biological norm constitute mental illness or moral depravity. The distinctive rhetorical and ideological advantage of this type of argument is that it is secular and supposedly objective. Those who oppose expanded rights for gender minorities but who do not have strong religious convictions typically pursue this line of argument. Recently I have seen this applied to transgenderism in particular, so that aspect of the argument is what I am focused on. 

First, a little background. This kind of thinking originated from centuries-old ideas about inherent differences between groups of people. Until recently, it was more often applied to race. Darwinism and early modern human biology emboldened those who held racist views. As religious fervor gave way to scientific rationalism, there conveniently arose a “scientific” justification for continuing oppression and slavery. While the details have changed, this biological theory of racial difference has continued to be a justification of racism today. However, it is less extreme now and less of a mainstream view. When feminism arose as a major force within public discourse in the 20th Century, it was met with a similar argument concerning biological difference (among other arguments). Again, these arguments still exist in a (mostly) milder form. This pattern was repeated again, more recently, with acceptance of homosexuality and equal marriage rights. We are now in the midst of a debate around acceptance of transgenderism and rights for trans people. So, what’s wrong with this kind of reasoning?

The Is-Ought Problem, also called Hume’s Guillotine, concerns the relationship between positive statements (“is” statements) and normative statements (“ought” or “should” statements). It’s impossible to make a connection directly from a descriptive statement about the world (“it is raining”) to a statement about what one should do (“I should carry an umbrella”) without related goal or moral rule that links them (“I don’t want to get wet”). It is possible for people to agree about a state of affairs while disagreeing about what to do about it because they have different goals or a different moral compass. 

For people who believe in moral facts (i.e., objective morality), there is supposedly a universal set of ready made is-to-ought bridges; however, the degree of radical disagreement among people as to what these facts are indicates that they are far from obvious and potentially unknowable. The result, then, is that people use their own judgment either way. Even if you believe that you have correctly identified moral facts, you must acknowledge that you used personal judgment to do so– for example, by coming to the conclusion that your particular religion is the correct one. As Jean-Paul Sartre says in Existentialism is a Humanism, “even if God did exist, it would make no difference [with respect to people having to decide for themselves what right and wrong are].” Additionally, for is-to-ought bridges to function logically, they must themselves be ought statements. It is not possible for a normative statement to have a purely positive justification. This can be characterized by an infinite regress of “why” questions, for example, “why should humans follow the will of God?” or, “why should humans do what makes them happy?” Even when the answer seems obvious or the question seems absurd, that is not an escape from the logical problem of justification.

When it comes to sex and gender, positive statements about human biology have no normative consequences in themselves. We can’t draw any conclusions about how we should behave except in relation to specific goals or moral values. In other words, the argument that a biological sex binary indicates that gender expression should also be a binary is a non sequitur. You must have an independent moral belief about this situation to serve as an is-to-ought bridge. The argument reduces completely to a disagreement about morality then; and if you believe that transgenderism is immoral, there is no need to appeal to biology. 

The idea that humans should do what is “natural” also incidentally falls under the Naturalistic Fallacy (or Appeal to Nature), which erroneously assumes that natural things are always better. Virtually everyone agrees that there are some ways in which it is better to live in a way that is “unnatural”, for example growing plants for food rather than gathering them from the wild. Alternatively, it can be said that all human behavior is “natural” since humans are themselves a part of nature. It cannot be the case that humans didn’t evolve to be homosexual or transgender, since this is in fact the way the population evolved to be– with some percentage of individuals being LGBTQ+. Every organism evolved to be exactly the way it is now by definition, even if it has maladaptive characteristics. 

Evolution has no teleological purposes or end goals. The purposes of structures and mechanisms identified in biology are features of human analysis and are of no concern to evolution. No body part was designed to operate a specific way, they simply do operate in specific ways that may ultimately be more or less adaptive. The idea of evolutionary progress, where organisms improve as time goes on (as opposed to merely change) is called orthogenesis. This was an early theory of evolution, even preceding Darwin (although it continued within Darwinism) and emerging out of medieval Christian scholars’ attempts to understand nature. Many of these scholars believed in a “chain of being” where all of existence is arranged hierarchically, from different types of angels to different minerals. Modern evolutionary theory, using genetic data and more recent paleontological discoveries, has established that evolution is in fact a highly complex and messy process with no goals or coherent direction. Organisms do not adapt in order to survive, but rather survive because they adapt. The vast majority of species fail to adapt and instead go extinct. Modern proponents of orthogenesis are largely the supporters of intelligent design or theistic evolution, hypotheses which, though not strictly impossible, are not at all supported by currently available scientific evidence. In any event, appealing to the will of God brings us back to the earlier problem– there is no need to make mention of evolution at all at that point, and the argument reduces completely to an argument about the will of God. While arguments about God are interesting, they are not within the scope of the current discussion.

This rather long and somewhat tangential discussion of evolution reiterates the point about the Is-Ought Problem. To summarize, arguments that appeal to biology fail because no part of biology has any normative consequences. The normative conclusion (i.e., that people should behave in certain ways) actually relies entirely on something external to anything biology says– whether it be belief in God, personal moral views, etc. Formally, such as argument has the following form:

• Premise 1) According to biology, x is true about human sexuality.
• Premise 2) If x is true about human sexuality, then humans should behave in way y.
• Conclusion) Therefore, humans should behave in way y.

One problem is that the focus tends placed on Premise 1– which is likely to be widely agreed upon –when the crux is Premise 2. Whether or not someone accepts Premise 1, Premise 2 is still likely to be the main area of disagreement if this argument is to be rejected. Premise 2 is often asserted without argument or left completely implicit, and moreover it is a purely normative proposition. It is completely independent of any positive statements about biology. In general, Premise 2 is no more convincing than the Conclusion– and as normative statements, they have the same logical status. If Premise 2 can be asserted without argument then the Conclusion can be asserted without argument, and the Premises become completely irrelevant. In other words, it boils down to a mere disagreement about morality (or norms). A focus on biology is therefore either misguided (the person making the argument does not understand the is-ought distinction) or it is a rhetorical appeal to scientific authority/consensus in order to mask the real crux of the issue (the person making the argument is intentionally using misleading reasoning). This shows the weakness of this type of argument from biology, since the argument as a whole is no stronger than just asserting the conclusion. 

The question of whether certain statements about biology are true is relatively unimportant, although showing the statement to be false will also defeat the argument. Generally speaking, the strength of such an argument is rhetorical only. It has the façade of an objective, scientific argument, while actually relying on the blunt assertion of a purely normative statement. Just like the biological justifications for oppression against people of color, women, and homosexuals, this line of reasoning will probably never go away completely. However, I also believe it will gradually fade from public discourse as acceptance for transgenderism grows. By now, the pattern is well-established.