Gender Theory: What Science Says

The expression “gender theory” — or “gender ideology” — is used in public debate to describe a supposed ideological project aimed at erasing differences between men and women, confusing children about their sexual identity, and dismantling the traditional family. This expression does not designate any existing scientific theory. It does not appear in any academic textbook, in any peer-reviewed journal, in any school curriculum. This article reconstructs where it comes from, what it distorts, and what scientific research actually says about gender identity.

Where the Expression “Gender Theory” Comes From

“Gender theory” does not originate in the academic world. It originates in the political and religious world, as a reaction to certain achievements in the field of civil rights and gender equality.

The Vatican Origins

The story begins in the 1990s, in response to the World Conference on Women in Beijing in 1995, during which the United Nations formalized the use of the concept of “gender” as an analytical tool for understanding inequalities between men and women. This development alarmed certain components of the Vatican, which saw in it a threat to the “natural complementarity” between the sexes.

In 1997, American Catholic journalist Dale O’Leary published The Gender Agenda, a book in which the concept of gender was compared to a “submarine” — a secret operation aimed at redefining equality against nature. The book had wide circulation in Vatican circles.

In 2003, the Pontifical Council for the Family published the Lexicon of Ambiguous and Debatable Terms on Family, Life and Ethical Issues, a collective work that dedicated extensive sections to criticizing the concept of “gender.” The following year, in 2004, the Congregation for the Doctrine of the Faith — led by then-Cardinal Joseph Ratzinger — published the Letter to the Bishops on the Collaboration of Men and Women in the Church and in the World, in which “gender” was presented as a current of thought that denies the sexual difference rooted in human nature (Source: [9]).

As jurist Mary Anne Case reconstructs in an article published in Signs: Journal of Women in Culture and Society in 2019, the Vatican’s war against so-called “gender ideology” has spanned decades, two papacies, and multiple fronts — from marriage equality to sex education, from transgender rights to anti-discrimination policies (Source: [2]).

The Spread Across Europe and the United States

From the Vatican environment, the expression “gender ideology” spread to conservative political movements across Europe. As sociologists Roman Kuhar and David Paternotte document in the volume Anti-Gender Campaigns in Europe (2017), anti-gender campaigns have manifested in at least eleven European countries, from France to Russia, from Italy to Poland, with mass protests, petitions, and media campaigns united by a common narrative: the existence of a dangerous “theory” that threatens children and the family (Source: [1]).

In the United States, similar rhetoric has been adopted by conservative organizations and political figures, particularly in debates over school curricula, bathroom access policies, and healthcare access for transgender people. The framing of gender studies as an “ideology” rather than an academic discipline has been used to oppose anti-discrimination legislation and inclusive education programs.

The term “gender ideology” does not describe an academic reality: it functions as a rhetorical device — a tool for transforming an established field of study into a bogeyman.

What Gender Studies Actually Are

Gender studies constitute an interdisciplinary academic field established for over fifty years. Born from the feminist movement and women’s studies of the 1970s, they have developed in universities worldwide as a research area that analyzes how gender categories influence social structures, power relations, institutions, culture, and individual experiences.

An Interdisciplinary Field

Gender studies draw from diverse disciplines: sociology, psychology, history, anthropology, political science, law, literature, medicine, neuroscience, biology. They do not constitute a single monolithic “theory” but a heterogeneous collection of approaches, methods, and perspectives, sometimes even in disagreement with one another.

Among the most influential contributions are those of Simone de Beauvoir, who in 1949 distinguished biological sex from socially constructed gender with the famous formula “one is not born, but rather becomes, a woman”; of Gayle Rubin, who in 1975 introduced the concept of the “sex/gender system”; and of Judith Butler, who in 1990 proposed the theory of gender performativity in Gender Trouble. None of these authors ever proposed “eliminating differences between men and women” or “confusing children.”

What They Concretely Study

Some examples of research conducted within gender studies:

• Wage gap: Why do women on average earn less than men in comparable roles with comparable skills?
• Gender-based violence: What cultural and institutional structures contribute to domestic violence and femicide?
• Health: How do gender norms influence access to healthcare, diagnosis, and treatment of diseases?
• Representation: How are men and women represented in media, advertising, and politics?
• Gender identity: What biological, psychological, and social factors contribute to the development of gender identity?

These are research questions — not a political agenda. The results are published in peer-reviewed journals, subjected to review by other researchers, discussed and replicated. This is the normal functioning of science.

The Difference Between “Gender” and “Sex”

One of the central misunderstandings of anti-gender narratives concerns the distinction between sex and gender. Those who speak of “gender theory” often claim that gender studies “deny” biological sex. In reality, the distinction between sex (a set of biological characteristics: chromosomal, gonadal, hormonal, anatomical) and gender (the set of social, cultural, and psychological meanings associated with these characteristics) is an analytical tool, not a denial of biology.

Recognizing that gender has a social dimension does not mean claiming that biological sex does not exist. It means recognizing that the way a society interprets and organizes sexual differences is not an immutable datum of nature but varies over time and across cultures. Biological sex itself is a more complex system than the simplification “male or female” suggests, as documented by research on variations in sex characteristics.

“Gender Theory” as a Straw Man

In rhetoric, a “straw man” is a fallacious argument that consists of distorting the opponent’s position to make it easier to attack. The expression “gender theory” works exactly this way.

What Is Attributed to “Gender Theory”

Those who use this expression typically attribute to it a series of claims:

• The sexes do not exist; gender is merely a social construction
• Children must be “confused” about their sexual identity
• Schools teach children to “change sex”
• The traditional family must be destroyed
• There is a global project to impose an ideology

What Gender Studies Actually Say

None of these claims finds support in academic literature. Gender studies:

• Do not deny biological sex. They study how biological characteristics interact with social norms.
• Do not propose confusing children. They advocate education in respect for differences.
• Do not aim to destroy the family. They study the plurality of family forms existing in different societies.
• Do not constitute a unified project. They are a heterogeneous field of research with different and sometimes contrasting approaches.

The distance between what is attributed to “gender theory” and what gender studies actually maintain is such as to make the term a textbook example of a fallacious argument.

What Science Says About Gender Identity

Gender identity — the inner sense of belonging to a gender — has been the subject of scientific investigation for decades. Research has produced a substantial body of evidence, published in high-profile journals and recognized by the world’s leading health institutions.

Biological Foundations

As documented in detail in the article on the biological foundations of gender identity, research has identified genetic, hormonal, neuroanatomical, and epigenetic contributions to the development of gender identity.

The review by Polderman and colleagues, published in Behavior Genetics in 2018, concluded that gender identity “probably reflects a complex interplay of biological, environmental, and cultural factors” and hypothesized that it is a multifactorial trait with a polygenic heritable component (Source: [4]).

A systematic review of twin studies published in Behavior Genetics in 2025 analyzed eight studies, seven of which provided evidence in favor of a genetic component of gender identity, with heritability estimates ranging from 0.10 to 0.81 (Source: [10]).

The 2021 ENIGMA study, the largest neuroimaging analysis ever conducted on transgender individuals, examined structural MRI data from 803 participants not undergoing hormonal treatment. The results showed that the brains of transgender individuals display their own distinct phenotype, not simply “intermediate” between male and female (Source: [6]).

Research in the field of epigenetics, such as the EWAS study published in Frontiers in Neuroscience in 2021, found that transgender and cisgender individuals have different DNA methylation profiles, with the most significant sites associated with genes involved in central nervous system development (Source: [11]).

These results do not establish simple biological determinism — gender identity is not “caused” by a single gene or a single factor. They do indicate, however, that it has real biological roots and is not the product of an ideology, a trend, or a voluntary choice.

The Consensus of Scientific Institutions

The world’s leading scientific and health institutions have taken positions on gender identity based on available evidence:

• The Endocrine Society, in its 2017 clinical guidelines, states that “considerable scientific evidence has emerged demonstrating a durable biological element underlying gender identity” (Source: [5]).

• The American Psychological Association (APA), in its 2021 resolution, reaffirmed that transgender and non-binary identities represent “normal variations in human gender expression” and opposed attempts to modify people’s gender identity (Source: [8]).

• The World Health Organization (WHO) reclassified gender incongruence in the ICD-11, removing it from the chapter on mental disorders and moving it to a new chapter dedicated to conditions related to sexual health. This reclassification reflects the scientific consensus that transgender identity is not a mental disorder (Source: [7]).

Gender identity is not an opinion, an ideology, or a political program. It is a subject of scientific study with converging evidence from diverse disciplines.

The “Gender Theory” Narrative in the United States

While the “gender theory” label originated in European political discourse, similar arguments have gained traction in the United States. Legislative efforts to restrict transgender healthcare access, ban discussion of gender identity in schools, and limit the rights of transgender individuals often rely on the same rhetorical framework.

The Debate Over Schools

In the United States, debates over school curricula have intensified, with some states passing legislation restricting discussions of gender identity and sexual orientation in classrooms. These legislative efforts often invoke the same arguments used in European anti-gender campaigns: that education about gender diversity amounts to “indoctrination” or “confusion” of children.

In reality, age-appropriate education about diversity and inclusion has been shown to reduce bullying, improve school climate, and support the well-being of all students, including those who are LGBTQ+. No school curriculum in the United States teaches children to “change their sex” or denies biological differences.

The Campaign Against Schools

The campaigns against the supposed “gender theory” in schools have been particularly intense in recent years, with organizations distributing materials to parents, organizing protests, and promoting legislation against educational projects that, in most cases, contain nothing of what is attributed to them.

As Garbagnoli documents (2017), these mobilizations are based on a systematic distortion of educational content: projects that discuss respect and inclusion are presented as “sexual indoctrination,” transforming education about diversity into a bogeyman (Source: [3]).

Why “Gender Theory” Works as a Narrative

If “gender theory” does not exist as a scientific theory, why has the expression been so successful? The answer lies in the very structure of the narrative.

A Vague and Omnipresent Enemy

The expression “gender theory” does not designate a precise content. Depending on the context, it can refer to sex education, the rights of LGBT+ people, feminism, sociology, psychology, research on sex differences. This vagueness is functional: an undefined enemy is harder to disprove than a specific one, because it can be continually redefined.

The Protection of Children as an Emotional Lever

Anti-gender campaigns systematically leverage parents’ concern for their children. The argument — “they want to confuse your children” — activates an emotional response that makes rational examination of the claims difficult. In reality, children develop an awareness of their own gender between ages 2 and 4, as documented in the developmental psychology literature. Education about differences does not “create” confusion: it helps children understand the diversity they already observe in the world around them.

Simplification as a Strategy

“Gender theory” works because it simplifies a complex body of knowledge into a caricature that is easy to attack. It is simpler to oppose an alleged project to “eliminate differences between men and women” than to engage with research on the biological foundations of gender identity, with epidemiological studies on the health of transgender people, or with evidence on how diversity education works.

Simplification is not a side effect of the anti-gender narrative: it is its central strategy.

Science Is Not an Ideology

One of the most problematic aspects of the “gender theory” narrative is that it transforms scientific research into an ideological position. If science becomes “ideology,” then it can be rejected with the same ease as a political opinion. But science does not work that way.

The evidence on the biological foundations of gender identity is not the product of an agenda. It is the result of decades of research conducted by thousands of researchers at universities and research centers around the world, published in peer-reviewed journals, replicated, and discussed by the international scientific community.

Rejecting this evidence is not an “alternative” position: it is an anti-scientific position, of the same kind as those that deny evolution, the efficacy of vaccines, or climate change. One can and should discuss the limitations of the research, the areas still open, the ethical implications of the discoveries. But denying the very existence of the evidence is an act of misinformation.

The Real Consequences of the Anti-Gender Narrative

“Gender theory” is not merely an academic issue. It has concrete consequences on people’s lives.

Every time the expression “gender theory” is used to delegitimize research on gender identity, it reinforces the stigma against transgender and non-binary people. Every time education about differences is presented as “indoctrination,” it becomes harder to combat bullying in schools. Every time gender identity is described as an “ideology,” it obstructs trans people’s access to the healthcare they need.

Trans people already face elevated rates of discrimination, violence, and psychological distress linked to social stigma. The “gender theory” narrative does not protect anyone: it fuels a cultural climate in which these people are perceived as a threat rather than as part of human diversity.

What We Can Do

In the face of misinformation, the most effective tool is accurate information. When someone mentions “gender theory,” some questions can help bring the conversation back to facts:

• “Which theory, exactly?” — The expression does not designate any scientific theory. Asking for specifics often reveals that what is being referred to is a caricature, not actual content.
• “Have you read the studies?” — Research on gender identity is public and accessible. Most people who talk about “gender theory” have never read a scientific article on the subject.
• “Who coined the expression?” — The expression does not come from science but from politics. Knowing its origin helps understand its function.

Science does not ask to be believed on faith. It asks to be read.

Related Articles

For further reading on the topics covered in this article:

• Gender Identity: Definition and Meaning — What “gender identity” means and how psychology and medicine define it.
• Common Myths About Trans People — Scientific analysis of the most widespread prejudices about transgender people.
• The Biological Foundations of Gender Identity — Genetics, neuroscience, endocrinology, and epigenetics: what we know.