Can thought be free in the 21st century? Recent developments suggest not. The penetration of the internet into every aspect of our lives has been accompanied by data harvesting on an extraordinary scale, enabling corporations and states to send us propaganda designed to target our personal weak spots. Advances in neuroscience, behavioural science and psychology have brought insights into the mind that make it seem increasingly capable of being manipulated.

Are our minds strong enough to withstand the continual interference we face every time we pick up our smartphones – in other words, to think freely? Two new books explore this question. To some extent, they draw on a shared body of scientific studies, as well as on wisdom gleaned from novelists and philosophers, notably George Orwell, Aldous Huxley and Plato. Even so, their approaches and conclusions are very different.

The more impressive of the two is The Battle for Thought, a wide-ranging study by Simon McCarthy-Jones, associate professor in clinical psychology and neuropsychology at Trinity College Dublin. While ‘the right to freedom of thought, conscience and religion’ is included in the Universal Declaration of Human Rights and was the subject of a report presented to the UN General Assembly in 2021, insufficient attention, McCarthy-Jones argues, has been paid to what that right entails and why it matters. Free thought is necessary to ‘win new truths’ and promote ‘personal autonomy and political self-government’, he says. It also contributes to human dignity, forms an essential part of our identities and offers a way of living beyond bodily comforts. As an academic who has also been an activist, he wants to replace the idea that thought is about privately ‘interpreting the world’, as suggested by Rodin’s Thinker, with the idea that its purpose is to change the world and that ‘the freest thought is social, not individual’.

Many psychological techniques, often covert, can be used to impinge on free thought, including distraction, confusion, pressure to compete and conform, and ‘nudging’, or the preferential presentation of one option over another. Government bodies and tech companies are supporting the development of brain-reading technologies, which, through the analysis of