Material girls: why reality matters for feminism, by Kathleen Stock, hardback, 312 pages, ISBN 978-0-349-72660-1, Little Brown, 2021, £16.99.

This is a splendid critique of the vexed theory of gender identity and of the unfortunate practices to which it gives rise. This theory is that we all have an inner feeling known as a gender identity and that this feeling is more socially significant than our biological sex.

One of the key inspirations of this theory is the American academic Judith Butler, who, as Professor Stock explains, "thinks there are no material facts before language - that is, prior to culturally specific linguistic and social constructions of them. Linguistic categories, including scientific and biological ones, aren't a means of reflecting existing divisions in the world, but a means of creating things that otherwise wouldn't have existed." This of course is the old, basic fallacy of idealism, which here, as elsewhere, opens the door to every kind of nonsense.

Stock continues, "According to Butler, scientific language in particular creates 'hierarchies' of domination and subordination, entrenching power relations between social groups." This leads directly to absurdities like Monique Wittig's jump to the claim that "there is no sex. There is but sex that is oppressed and sex that oppresses. It is oppression that creates sex and not the contrary."

It also leads to trans scholar Jack Halberstam's claim that we create concepts because of our 'mania for a godlike functioning of naming … [which] began… with colonial exploration'. Professor Stock observes calmly that "in fact the capacity to name and conceptualise the world in interest-relevant ways has been with humans for as long as their higher cognitive brain functions have. We wouldn't have got very far without it."

As against Judith Butler, Professor Stock asserts that there is "no serious challenge to the idea of two natural, pre-given sexes. There is a naturally occurrent division of humans into males and females. Over 99 per cent of humans fall unambiguously into one category or the other … As binaries in nature go, the sex division is one of the most stable and predictable there is. In the vast majority of cases, sex is not 'assigned at birth' but detected - in most cases via observation at birth, and in a few cases later on. Despite wording of UK laws such as the Gender Recognition and Equality Acts, sex cannot be 'reassigned' through surgery or a change in legal status, nor 'changed'."

As Professor Stock points out, "Gender identity theory doesn't just say that gender identity exists, is fundamental to human beings, and should be legally and politically protected. It also says that biological sex is irrelevant and needs no such legal protection."

Using this flawed theory, the LGBT charity Stonewall now advises, "You should allow anyone to access facilities, spaces and groups which align with their gender identity." This would allow trans men to access every women-only facility - refuges, changing-rooms, toilets, etc.

Professor Stock rightly asserts that "there are no circumstances in which minors should be making fertility- and health-affecting decisions involving blockers, hormones or surgery, as is now happening in many countries."

"we should at least be clear that TRANS WOMAN, TRANS MAN, WOMAN and MAN are four different concepts, each with different membership conditions; and that membership of TRANS WOMAN doesn't entail membership of WOMAN or preclude membership of MAN, and nor does membership of TRANS MAN entail membership of MAN or preclude membership of WOMAN." (Professor Stock capitalised these words, as she explains, to indicate that she is referring directly to the concepts, not to the entities to which they refer.)

Otherwise, more absurdities follow, for example, 'Police forces let rapists record their gender as female', as reported in The Times, 20 October 2019.

Stonewall defines 'transphobia' as "The fear or dislike of someone based on the fact they are trans, including denying their gender identity or refusing to accept it." This is to conflate fact and value, to jump from a statement about identity to a condemnation of that statement.

Similarly, as Professor Stock writes, too many people "tend rhetorically to collapse criticism of the intellectual tenets of trans activism into moral criticism of trans people." As a result, all criticism of certain propositions is forbidden as just an expression of personal dislike.