But activists became convinced that this was the wrong way around, that housing is a right and people will only pull themselves together once they’ve got a roof over their heads. Anything less than the offer of permanent accommodation is an insult and a waste of time.

As the provision of shelter fell out of favour, however, land values in San Francisco continued to rise, making it harder for city officials to expand the stock of living spaces. Today both housing and shelter are insufficient, leaving people to sleep in doorways instead.

The perfect is the enemy of the good. Take mental health. Liberals will readily tell you that the streets are full of sick people because Ronald Reagan cut funding for mental institutions, yet Shellenberger points out that they were shut by Democrats, too – to save money and because activists got it into their head that any form of asylum, even the most gentle and progressive, was wrong. 

For instance, in 2004 Californians voted to spend over $2 billion extra on mental health provision – exempting involuntary incarceration, which meant the money was splashed on middle-class services such as exercise classes and gardening. Meanwhile, the very sick, unable to care for themselves and a danger to others, graduated from asylums to prisons, or self-medicating on the streets.

When it comes to the war on drugs, painted by the Left as authoritarian and racist, Shellenberger argues that though there has been a sharp rise in incarceration generally, “only 20 per cent of prisoners in all jails and prisons are there for drugs”. Violence drove a prison boom, stricter drug sentences less so, and if drugs were legalised overnight, this would have a negligible effect upon the racial make-up in prisons.

The real problem, suggests the author, is the refusal to prosecute the war on drugs. San Francisco has effectively gone down the route of decriminalisation, and become a safe space for addicts and pushers.