«Those who cannot understand the past are condemned to repeat it. »Every one of us knows that we are fallible.

But to what extent?Sure, we can be mistaken sometimes, but certainly not on anything really important: we do, after all, understand the world around us and have fine enough decisional skills. Or do we?Descartes hypothesized the existence of an evil demon, an entity that is “as clever and deceitful as he is powerful, who has directed his entire effort to misleading me”.

He can alter both my senses and the laws of logic. In such a case, anything I could ever learn and know will be nothing but an illusion.

We don’t really care that much about this idea: it’s nothing but a philosophical speculation and, although theoretically preoccupying since it cannot be disproven, we can practically just assume it to be wrong and go along with our life. We should however take seriously an other hypothesis: there could be a “Subtle” Evil Demon, not so almighty but equally deceptive.

He wouldn’t be capable to alter the external reality and create an illusory world, but it could alter our perception from time to time. This book explores the secrets and deceptions of this Subtle Evil Demon: our own brain, and all the many different ways it manipulates our understanding of reality, convinces us to believe false things and prevent us from realizing what is really going on.

We will discuss optical illusions, flaws in our perception, false memories, hidden factors that influence our decision without our notice, and many psychological mechanisms that are strange, surprising… and even dangerous. We tend to assume that people makes mistakes due to a lack of intelligence, knowledge or insight.

However, most of wrong things people believe and do depends on our natural thinking and decisional patterns. They are the consequence of how the Subtle Evil Demon manipulates our mind into a false understanding of reality.

If we miss this crucial fact, we will never be able to fix it and create a better world. In the past, people have blindly believed in theories we consider to be utter irrational nonsense, and the consequence of this have often been violence, discrimination, suffering and death.

We must realize that, in order to prevent this to happen anymore, we must open mindedly accept a scary, but realistic idea: «Those horrible events happened because those people thought and acted exactly in the same way as I do today»This book will uncover our own brain’s many flaws and natural errors, and discuss deeply the suffering that can follow any time we blindly trust the Subtle Evil Demon. .