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The Great Mental Models Volume 2

Physics, Chemistry and Biology

By Shane Parrish, Rhiannon Beaubien
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The Great Mental Models Volume 2 by Shane Parrish, Rhiannon Beaubien

The Great Mental Models Volume 2 (2019) is all about the art of making unexpected connections. Rooted in the “hard” sciences, it unpacks core concepts from physics, chemistry, and biology. But it’s not only about electrons, elements, and evolution. The ideas covered in this fascinating intellectual history can also be applied to everyday life.

Key idea 1 of 8

When it comes to social change, mass matters.

Paris, 1905. The cafés are full. Waiters bustle from table to table setting down small glasses of green liquor. The smell of aniseed fills the air.

The beverage being served is absinthe – a fashionable aperitif that became notorious for its potency.

In the early twentieth century, newspapers began running sensational stories about absinthe’s effects. It’s as addictive as opium! It drives drinkers insane! The stories cited the case of Jean Lanfray, a man who murdered his family in an absinthe-fueled rage. People began to campaign against absinthe, insisting that it be outlawed. 

Meanwhile, not much was being written about lead, a toxic metal that was used to make the pipes that conveyed drinking water. Lead was present in hundreds of other products, too, from paint to glassware to makeup. But, despite its dangers, there was no campaign to ban lead.

The key message in this blink is: When it comes to social change, mass matters. 

The claims about absinthe were bunk. It wasn’t any more harmful than other high-percentage alcohols, and it certainly didn’t drive you mad. But the writing was on the wall after Lanfray’s “absinthe murders.” Switzerland banned it in 1908; France followed in 1914.

Lead was different. The evidence against it wasn’t overstated – it was simply ignored. The Roman architect Vitruvius had warned his contemporaries against putting water in lead pipes around 15 BCE. In the 1910s, the American industrial toxicologist Alice Hamilton provided definitive proof of the dangers of lead exposure. It didn’t matter: lead continued to be added to paints and gasoline well into the 1980s.

So what explains the different reactions to absinthe and lead? 

Physics can help us answer this question. Take the concept of inertia, which describes the resistance of objects to changes in their state of motion. Stationary objects remain stationary and moving objects continue moving unless they meet an opposing force like propulsion or friction. Mass matters here. The larger the object, the more force is needed to move or stop it.

Substances like lead and absinthe have a kind of “societal mass,” and the same rule applies. Lead had been used for millennia and “stopping it” – that is, getting rid of it – meant changing everything from how walls were painted to how cars were fueled. Absinthe, by comparison, was a lightweight: it hadn’t been around long and all it did was get people drunk – something other liquors did just as well without appearing to drive men to murder their families. Lead, in other words, had lots of societal mass while absinthe had very little.

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