“Being old enough to die is an achievement not a defeat, and the freedom it brings is worth celebrating.”

From this striking vantage point, Barbara Ehrenreich, in her recent book Natural Causes: Life, Death and the Illusion of Control, considers the way our perspectives on life, health, our bodies, and our minds are constructed through metaphor and social convention. This is not a passive, neutral, or value free process. Where and what are our bodies and ourselves in these anxious, consumerist times?

Although best known as a writer and campaigner on social and political topics, Ehrenreich began her career as a PhD student working on the immune system, “a magical and for the most part invisible cloak.” She worked on macrophages in particular, which were conceived as “frontline defenders” against invaders. She notes that military metaphors for the immune system are common: for example, “fighting disease;” “battling infection;” or guard animals, the “big eaters” that devour invaders.

So far, so conventional, but what to make of the more recent discovery that macrophages, whose accumulation at the site of tumours had been assumed to be part of the body’s “heroic” resistance, may actually facilitate the spread of malignancy—themselves, committing “cellular treason.” Macrophages are “cheerleaders on the side of death,” providing tumour cells with access to blood vessels and hence metastasis to distant sites. Researchers are “horrified” by this behaviour.

In this metaphor of treason, who is rebelling against what? Who is in charge? Can we control our minds, bodies, and lives, and if we can, who is controlling what? She argues that, to replace religious belief and the flight of the soul, we have a new model of “the self,” which centres around the mind controlling the body, a struggle between mind and body, and the body as something to be worked on. This work includes eating the right food and fitness regimes. Witness the rise of fitness regimes as a marker of virtue and the elision of health behaviours with class identity.

But now the mind itself has become something to control. Ehrenreich describes how mindfulness is offered as a solution to the developing problem of the distraction caused by technology, and is itself being marketed to us by the tech industry—selling apps as a solution to a problem it has created. “Neuroplasticity” is the advertising tagline replacing the less sophisticated concept of “brain training.” The mind is to be controlled through disciplined exercise, much as the body should be.

Or not. So keep fit, eat well, and be lucky. Wellbeing may be yours, but be careful of analogies, especially ones of violence and discipline.

From professor of immunology, Sheena Cruickshank, who appeared on The Life Scientific recently, a final and more encouraging metaphor: “the primary job of the immune system is actually maintaining tolerance.”

Nicholas Hopkinson, reader in Respiratory Medicine, Imperial College London.

Competing interests: None declared.