The Little Leaflet on “The Book of Why: The New Science of Cause and Effect”

Judea Pearl and Dana Mackenzie provide an illuminating examination of the resurgence of causal reasoning across science and artificial intelligence in The Book of Why.

Rich Brown
4 min readJul 22, 2023
Lightbulb moments representing flashes of causal understanding
Lightbulb moments representing flashes of causal understanding

For centuries, science focused on statistical associations and correlations revealed in data. However, determining cause-effect relationships allows much deeper insight and more rigorous reasoning. In The Book of Why, computer scientist Judea Pearl and science writer Dana Mackenzie compellingly argue causal thinking is experiencing a profound renaissance.

The authors begin by exploring philosophy and history. Greek philosophers like Aristotle analyzed causal principles. However, Scottish philosopher David Hume later argued causal relationships could not be definitively proven through empirical facts alone. This led science to shy away from speculating about causality, instead sticking to descriptive correlations in the data.

A maze being solved step-by-step following causal chains
A maze being solved step-by-step following causal chains

Pearl explains how he pioneered modern computational causal inference. His key innovations included causal diagrams using directed acyclic graphs to map hypothesized causal links between variables visually. This reflects the fact that causal relationships have direction — the cause precedes the effect. Pearl also developed Bayesian statistical techniques like do-calculus and structural equation modeling to rigorously test if causal models align with observed data.

The book covers exciting applications of these techniques. In medicine, discovering causal mechanisms allows more effective interventions. For example, the correlation between smoking and cancer is well known. But more advanced analysis revealed nicotine specifically causes lung adenocarcinomas through a cascade of genetic mutations. This insight suggested targeting those genes could treat this cancer in nonsmokers.

Pearl also demonstrates uses in AI and machine learning. Standard deep learning algorithms only capture statistical patterns in data. But integrating causal models and reasoning enriches their understanding significantly. The book envisions an AI assistant that not only makes recommendations based on correlations, but also explains the causal logic behind its suggestions when asked.

Lightbulb moments representing flashes of causal understanding
Lightbulb moments representing flashes of causal understanding

Importantly, the authors stress causal conclusions require human judgment and domain expertise in addition to data analysis. They warn against overeager embrace of pure big data approaches, which can unearth spurious correlations. Causal models provide essential context.

To demonstrate this danger, Mackenzie humorously analyzes data showing areas with more storks have higher birth rates. But rather than storks delivering babies, the true hidden cause is heightened human population density driving both phenomena. This illustrates how correlations alone can lead to absurd conclusions when causal mechanisms are ignored.

The book examines economic applications like targeted interventions to assist the poor rather than ineffective broad programs. It also covers unintended side effects. For example, while aspirin relieves headaches, it can also dangerously cause intestinal bleeding undetectable from surface correlations alone. Only identifying this underlying causation revealed the full picture.

Pearl believes embracing causality can launch a new scientific revolution. He envisions disciplines like education, social science, public policy, law, and business benefiting tremendously. However, the transition may be bumpy. Scientists and engineers must refresh their education to master these methods. Integrating causal thinking into AI also remains challenging.

A maze being solved step-by-step following causal chains
A maze being solved step-by-step following causal chains

The authors conclude that unraveling the tangled causal knots of reality offers immense opportunities. New software tools democratize discovering causal relationships from data. However, human oversight of AI’s causal reasoning remains critical. Pearl believes capitalizing on this mathematical breakthrough while emphasizing ethics can hugely benefit society across domains.

In providing this accessible introduction, The Book of Why makes a convincing case for causality’s central role enriching science and technology. Pearl and Mackenzie artfully balance technical explanations, illustrative examples, and enthusiastic speculation about future potential. Their book offers an outstanding overview of transformative ideas poised to engineer a more prosperous, informed, and just world once wisely implemented. This leaflet summarizes the core concepts and importance of this visionary book.

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Rich Brown
Rich Brown

Written by Rich Brown

Passionate about using AI to enhance daily living, boost productivity, and unleash creativity. Contact: richbrowndigital@gmail.com

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