To be human is to suffer from a peculiar congenital blindness: On the precipice of any great change, we can see with terrifying clarity the familiar firm footing we stand to lose, but we fill the abyss of the unfamiliar before us with dread at the potential loss rather than jubilation over the potential gain of gladnesses and gratifications we fail to envision because we haven’t yet experienced them. 

Unless you’ve had the relevant experiences, what it is like to be a person or an animal very different from yourself is, in a certain fundamental way, inaccessible to you. It isn’t that you can’t imagine something in place of the experience you haven’t had. It’s that this act of imagining isn’t enough to let you know what it is really like to be an octopus, or to be a slave, or to be blind. You need to have the experience itself to know what it is really like.

This brings out another, somewhat less familiar fact about the relationship between knowledge and experience: just as knowledge about the experience of one individual can be inaccessible to another individual, what you can know about yourself at one time can be inaccessible to you at another time.