Why

Preface

Will drinking coffee help you live longer? Who gave you the flu? What makes a stock’s price increase? Whether you’re making dietary decisions, blaming someone for ruining your weekend, or choosing investments, you constantly need to understand why things happen. Causal knowledge is what helps us predict the future, explain the past, and intervene to effect change. Knowing that exposure to someone with the flu leads to illness in a particular period of time tells you when you’ll experience symptoms. Understanding that highly targeted solicitations can lead to political campaign donations allows you to pinpoint these as a likely cause of improvements in fundraising. Realizing that intense exercise causes hyperglycemia helps people with diabetes manage their blood glucose.

Despite this skill being so essential, it’s unlikely you ever took a class on how to infer causes. In fact, you may never have stopped to think about what makes something a cause. While there’s much more to the story, causes basically increase the chances of an event occurring, are needed to produce an effect, or are strategies for making something happen. Yet, just because a medication can cause heart attacks does not mean that it must be responsible for a particular individual’s heart attack, and just because reducing class sizes improved student outcomes in one place does not mean the same intervention will always work in other areas. This book focuses on not just what inferences are possible when everything ...