The Elephant.......................

 So what, exactly, is the elephant in the brain, this thing we're reluctant to talk and think about?  In a word, it's selfishness—the selfish part of our psyches.

     But it's actually broader than that.  Selfishness is just the heart, if you will, and an elephant has many other parts, all interconnected.  So throughout the book, we'll be using "the elephant" to refer not just to human selfishness, but to a whole cluster of related concepts:  the fact that we're competitive social animals fighting for power, status and sex; the fact that we're somethings willing to lie and cheat to get ahead; the fact that we hide some of our motives—and that we do so in order to mislead others.  We'll also occasionally use "the elephant" to refer to our hidden motives themselves.  To acknowledge any of these concepts is to hint at the rest of them.  They're all part of the same package, subject to the same taboo.

-Kevin Simler and Robin Hanson,  The Elephant In The Brain