this changed in the 17th century with this great philosopher, mathematician, rene december katrina, descartes, who developed a different view of pain .. he thought of pain as a biological process and drew this wonderful drawing of a young boy being burnt. his toes being injured, and finers were carrying the information about injury directly from the toe into the brain, although the details of this model are not what we view as the pain process the general idea that it is a biological process is the current view. but the question is, what is the nature of the biological process. it is remarkable to realize that until 20 years ago, we did not have a good understanding until -- of the nature of the biological process involved. people thought that pain was very different from all of the instrumentalities, for each modality you have different receptors like rods and cones in the rhett na, you have old factory receptors old factory receptors in the nose .. each one has a private line, receptors specific to it and nerve fibers that lead to it. >> rose: hear, feel, touch. >> exactly, with pain people