From Virtual Reality by Howard Rheingold, Simon & Schuster, 1991, pp27-28
(as quoted by Haptics, a South African multimedia design company)

'Haptic perception involves the melange of senses we lump together under the
category of "touch", but haptic is not strictly tactile in the same way ones fingertips
convey tactile information about the outside world; rather, haptic tasks like landing a
fish or docking a molecule also use the body's internal sense of proprioception that
informs us about the position of our own limbs in relation to one another and to the
space around us.

'Human proprioception includes a system of internal sensors at joints and in muscles
to detect changes in pressure and position. A higher-level processing system
detects significant patterns among the messages from the body's proprioceptors (eg
this pattern of messages from this particular set of sensors means that your body is
going to topple forward if you don't do something about it; that pattern of messages
means that your are pushing something heavy and polished across a low-friction
surface).

Proprioception's third information system consists of the effectors for transmitting
commands from the sensing and sense-making systems to the muscles - the
microadjustments that keep us upright and guide our movements. Part of daily life
that is so ordinary we hardly notice it is the fast, silent, information-processing and
fine muscular co-ordination skill that enables you to move your hand in exactly the
right direction when you decide to reach for a glass of water. A ballet dancer is a
virtuoso of proprioception. Haptics involves both proprioceptive and tactile senses,
in concert with other senses.

'...In a human-computer haptic system, the human is the part of the system that finds
the significant patterns; the haptic part translates invisible forces to human-sensible
form.'