這是科學家所稱之為「說明深度的假象」（illusion of explanatory depth）：我們往往對於日常生活事物背後的複雜理論或運作邏輯一知半解。人們總認為自己十分了解這個世界，事實上，當他們被要求試著說明特定概念時，才發現自信只不過是假象。知識的共享性，常讓人誤認為個人所知較實際上更多，實則不然；相對而言，智慧的總合讓人類得以達成不可能，不管是創建民主制度、登陸月球，或是完成基因組定序。人類個體並不完美，但集合眾人智慧將導向意想不到的結果！
Human reasoning is remarkably shallow - in fact, our thinking and justifications just scratch the surface of the true complexity of the issues we deal with. The ability to think may still be the greatest wonder in the world (and beyond), but the way that individuals think is less than ideal.
In The Knowledge Illusion, Sloman and Fernbach show that our intelligence resides not in individual brains but in the collective mind. To function, individuals rely not only on knowledge that is stored within our skulls but also on knowledge stored elsewhere, be it in our bodies, in the environment or especially in other people. Put together, human thought is incredibly impressive, but at its deepest level it never belongs to any individual alone.
And yet the mind supports the most sublime, incredible phenomenon of all: consciousness. How can any of this be possible with a mind that is so imperfect? This is one of the key challenges confronted in this book. The Knowledge Illusion ties together established scientific facts whilst also considering what the mind is for. Understanding why the mind is as it is, and what it is for, will show why we need to consider it as extending beyond our skulls; why we should think about 'the mind' as far more than an extension of the brain but as an emergence from multiple brains interacting. Simply put, individuals know relatively little, but the human hive that emerges when people work together knows a lot.