Some emotions are easier to fake than others, and some are easier to hide than others. La Rochefoucauld says that as a general matter it is harder to disguise emotions we have than to pretend to have those we do not. The truth of this matter seems to require a big qualifying “it depends.” It depends on which feelings we are trying to cover up and which we are trying to feign. It is much easier to disguise what Hume called the calm passions than to disguise the violent ones. I can cover up benevolence more easily than my sense of disgust, my sense of satisfaction in a beautiful object more easily than my grief. And though it is not hard to feign interest, concern, amusement, and other emotions that are commonly feigned in routine conversation, one can almost choke at times trying to feign delight in the unexpected arrival of a visitor or in a colleague's big raise.

Some emotions are characterized by postures and facial expressions that are easy to fake: joy, surprise, female sexual pleasure, anger, disgust. Very few are impossible to fake in some way, and that is a very good thing. If we had to rely on really feeling an emotion to display it, most of us would have been murdered long ago by people we offended. Imagine, as an evolutionary fantasy, that the signs of our emotions and other inner states were unfakeable or unveilable.