[Music]
imagine a brilliant neuroscientist named
Mary Mary lives in a black-and-white
room she only reads black and white
books and her screens only display black
and white but even though she has never
seen color Mary is an expert in color
vision and knows everything ever
discovered about its physics and biology
she knows how different wavelengths of
light stimulate three types of cone
cells in the retina and she knows how
electrical signals travel down the optic
nerve into the brain there they create
patterns of neural activity that
corresponds to the millions of colors
most humans can distinguish now imagine
that one day Mary's black and white
screen malfunctions and an apple appears
in color for the first time she can
experience something that she's known
about for years does she learn anything
new is there anything about perceiving
color that wasn't captured in all her
knowledge philosopher Frank Jackson
proposed this thought experiment called
Mary's room in 1982 he argued that if
Mary already knew all the physical facts
about color vision and experiencing
color still teaches or something new
then mental states like color perception
can't be completely described by
physical facts the Mary's room thought
experiment describes what philosophers
call the knowledge argument that there
are non physical properties and
knowledge which can only be discovered
through conscious experience the
knowledge argument contradicts the
theory of physicalism which says that
everything including mental states has a
physical explanation to most people
hearing Mary's story it seems
intuitively obvious that actually see in
color will be totally different than
learning about it therefore there must
be some quality of color vision that
transcends its physical description the
knowledge argument isn't just about
color vision Mary's room uses color
vision to represent conscious experience
if physical science can't entirely
explain color vision then maybe it can't
entirely explain other conscious
experiences either for instance we could
know every physical detail about the
structure and function of someone else's
brain but still not understand what it
feels like to be that person
these ineffable experiences have
properties called qualia subjective
qualities that you can't accurately
describe or measure qualia are unique to
the person experiencing them like having
an itch being in love or feeling bored
physical facts can't completely explain
mental states like this
philosophers interested in artificial
intelligence have used the knowledge
argument to theorize that recreating a
physical state won't necessarily
recreate a corresponding mental state in
other words building a computer which
mimicked the function of every single
neuron of the human brain won't
necessarily create a conscious
computerized brain not all philosophers
agree that the Mary's room experiment is
useful in me some argue that her
extensive knowledge of color vision
would have allowed her to create the
same mental state produced by actually
seeing the color the screen malfunction
wouldn't show her anything new
others say that her knowledge was never
complete in the first place because it
was based only on those physical facts
that can be conveyed in words years
after he proposed it Jackson actually
reversed his own stance on his thought
experiment he decided that even Mary's
experience of seeing red still does
correspond to a measurable physical
event in the brain not unknowable qualia
beyond physical explanation but there
still isn't a definitive answer to the
question of whether Mary would learn
anything new when she sees the Apple
could it be that there are fundamental
limits to what we can know about
something we can't experience and would
this mean that there are certain aspects
of the universe that lie permanently
beyond our comprehension or will science
and philosophy allow us to overcome our
minds limitations
[Music]
you