The illustrated principle by which we can apply reason to improve human welfare may seem obvious and old-fashioned, but it is not. Especially today, the ideals of reason, science, humanism, and progress need to be defended unconditionally. We take their gifts for granted, forgetting that these are not cosmic birthrights, but human achievements. In some less fortunate parts of the world, war, scarcity, disease and ignorance are a natural part of existence. We know that it is possible to return to those primitive conditions. Forgetting the importance of human progress can generate a corrosive fatalism, capable of destroying the precious institutions that guarantee this progress inspired by the Enlightenment, such as liberal democracies and organizations of international cooperation.
The ideals of the Enlightenment are products of reason, but they always struggle against other aspects of human nature: loyalty to the tribe, deference to authority, magical thinking.
This book attempts to reaffirm the ideals of the Enlightenment with the language and concepts of the 21st century, to provide a framework for understanding the human condition —who we are, where we come from, what our challenges are, and how we can face them— based on modern science and data.