- Understanding mental representation: This too is indispensable if we
are to make sense of what happened to the thief and the police
officer. To us witnesses of what happened, she saw that the man
had dropped his hat and wantedto give it back to him. He thought
she knewhe had broken into a house. But she in fact did not know
that, although she immediately deducedwhat was going on when
she saw the jewels. She also realizedthe thief had not understood
that she only wantedto help him.... One could go on for some
time. The point is that you cannot understand the story if you do
not maintain a rather sophisticated account of who thinks what
[98] about whom. But thoughts are invisible. You cannot observe them
directly, you have to infer them.
This is not, by far, a complete list of all the systems engaged, but it
should be enough to give an idea of what I want to emphasize here.
The most banal scenes of everyday life are replete with facts that
seem obvious or simple only because we have a veritable Pemberley
in the head, a huge mental basement filled with extremely efficient
servants, whose activities are not available for detailed conscious
inspection. Each of these specialized systems only handles a limited
aspect of the information available about our surroundings but pro-
duces very smart inferences about that aspect. This is why all these
systems in the brain are called inference systems.
This is where scientific discoveries go against the grain of com-
mon sense. We may think that there is nothing terribly complicated
in understanding, for instance, how objects move when they are
pushed, what happens when they collide, why an object will fall if
there is nothing underneath to support it—in other words what psy-
chologists call "intuitive physics." If I drop an object, you expect it to
fall downward with a vertical trajectory. If I throw a ball against a
wall, you expect it to bounce at an angle that is roughly symmetrical
to that at which it hit the wall. If a billiard ball is on the path of
another billiard ball, you expect them to collide, not go through one
another. If you throw a tennis ball as hard as you can, you expect it to
fly higher and faster than if you just gave it a gentle nudge. Intuitive
physics, like its scientific counterpart, is based on principles. These
principles take as input a particular description of what objects are
around and what their motion is, and produce expectations about the
next step. That we have precise expectations is not something we are
aware of. It is made manifest only when some aspect of physical real-RELIGION EXPLAINED