tain panoply of inference systems is what we mean when we say that it
belongs to a particular category.
To return to the thief and the police officer: you formed certain
expectations about the physicsof the dog and the old man. So when
their trajectories coincided you were not surprised that they collided
(rather than going straight through one another). So we can say that
looking at the dog and the man had activated your intuitive physics sys-
tem. This system is activated also when you look at inert objects like
trees or at man-made objects. But the dog and the man and the police
officer also activated your goal-detectionsystem, which is why you
[100] could spontaneously assume that the dog was trying to catch the cat,
the man was trying to avoid the dog, and the police officer was trying
to catch up with the man. These persons also activate a more compli-
catedintuitive psychology system, which produces subtle inferences such
as "she realized that he had not realized that she did not know what he
was up to"—a description that would never be produced if you were
considering a tree, and might be produced in a much simpler form if
you were considering a mouse or a worm. That the screwdriver was
hard and sharp would be an expectation of your structure-functionsys-
tem. This system is also activated by animal or human body-parts: see-
ing a cat's claws you immediately expect them to be there so that the
animal can rip open its prey's body. On the other hand, when you see a
tool, you immediately activate a description not only of its functional
features but also of its use by a human hand—for instance the fact that
a screwdriver or gimlet is designed to be turned whereas a crowbar is
meant to be pressed down on.
All this to show that you can replace what I called "ontological cat-
egories with theories" with a list of appropriate inference systems. If
something activates physics, goal-detection, as well as some biological
expectations I will describe below, then it is what we usually call an
"animal." If it activates all that plus intuitive psychology, it is what we
usually call a "person." If it activates physics and structure-function, it
may be either a "man-made object" or an "animal part." If in addition
it activates intentional use, it is what we usually call a "tool." Instead of
having a complex mental encyclopedia with theoretical declarations
about what animals and artifacts and persons are, all we have are flags
that switch on particular systems and turn other systems off.
Our knowledge of inference systems has recently made huge
progress because of independent findings in four different fields.
Experimental studies of normal adult subjects showed how their intu-
RELIGION EXPLAINED