Pitts, Walter

Walter Pitts was born in 1923, vanished from the scene in the late 1950s, and died at the end of the 1960s, having destroyed, as much as he could, any traces of his past existence. He is a peculiarly difficult subject for a biography because, although he remains a vividly haunting memory to those who knew him, he seems only a group delusion to others. At least that was the opinion of the neurologist Norman GESCHWIND.

Pitts appeared as a penniless 14-year-old at the University of Chicago in 1937, attended various classes, though unregistered, and was accepted by Rashevsky's coterie as a very talented but mysterious junior. All that was known of him was that he came from Detroit, and that would be all that was known thereafter.

An autodidact, he read Latin, Greek, Sanskrit, and German (though did not speak them) and apparently was advanced well beyond his years in LOGIC. The last can be illustrated by a confirmable anecdote. In 1938 he appeared at the office of Rudolf Carnap, whose most recent book on logic had appeared the previous year. Without introducing himself, Pitts laid out his copy opened to a section annotated marginally, and proceeded to make critical comments on the material. Carnap, after initial shock, defended his work and engaged with Pitts in an hour or so of talk. Pitts then left with his copy. For several weeks, Carnap hunted through the university for "that newsboy who understood logic," finally located him, and found a job for him, for Pitts had no funds and lived only on what he could earn from ghosting papers for other students.

In 1938, Pitts, Jerry Lettvin, and Hy Minsky (the future economist) formed a friendship that would endure over the years. When Lettvin went to medical school in 1939 at the University of Chicago, they would still meet often. In 1941, Warren MCCULLOCH came to the University of Illinois from Yale and Gerhardt von Bonin introduced Pitts and Lettvin to him. Thereafter Pitts joined the laboratory unofficially.

Pitts was homeless, Lettvin wanted to escape his family, and so McCulloch, together with his remarkable wife Rook, in spite of having four children already, brought the pair into their household. In late 1942, after weeks of reviewing the material in neurophysiology, Pitts told McCulloch of Leibniz's dictum that any task which can be described completely and unambiguously by a finite set of terms can be performed by a logical machine. Six years earlier TURING had published his marvelous essay on the universal computing engine. The analogy of neurons (as pulsatile rather than two-state devices) to the elements of a logical machine was inescapable. By 1943 McCulloch and Pitts published their famous paper, "A Logical Calculus of the Ideas Immanent in Nervous Activity." In 1947 they added the work "How We Know Universals." It was an attempt to interpret the structure of cortex as providing the sort of net that could abstract form independent of scale.

In 1943 Pitts, visiting Lettvin (who was interning in Boston), met Norbert WIENER and was invited to come to MIT as a research assistant. By the beginning of 1944, Pitts had been taken by the Kellex Corporation (a branch of the atomic bomb project). In the late 1940s he returned to MIT and began a project extending the work of Caianiello (on two-dimensionally connected nets) to three-dimensionally connected arrays -- an extremely difficult problem.

In 1951, Jerry Wiesner, at the behest of Wiener, invited McCulloch, Patrick Wall, and Lettvin to join the Research Laboratory of Electronics (RLE) as research associates. Despite the loss of status and income, the three accepted with the full enthusiasm of their wives. They and Pitts formed a new laboratory at RLE.

But in late 1952, Wiesner received a letter from Mexico City where Wiener and his wife were visiting Arthur Rosenblueth. Viciously phrased, it severed all relations with McCulloch's group, which included Pitts. Only after a decade did Rosenblueth reveal what had set off this explosion. It had nothing to do with any substantive cause but was the result of a deliberate and cynical manipulation designed to sever Wiener's connection with McCulloch and his group. The details are not edifying; Wiener was victimized as much as the group.

The effect on Pitts was devastating; he was the most vulnerable. Wiener had become the father he had never had. From that point on, Pitts went into a steep decline. He abandoned interest in the work, and though willing enough to help, lost all initiative. Nothing could be done to arrest his decline. Pitts would have nothing to do with any psychiatrist, even those whom he met at the Macy symposia and other such roundtables. He destroyed all of his past work that he could find and became a ghost long before he died.

On a personal level, Pitts was a wonderful friend, and an inexhaustible fount of knowledge about everything, the arts as much as the sciences. One asked him a serious question only if there was enough time to hear the full answer, which was sometimes several hours long, but never didactic, rather, extremely witty and tailored to the understanding of the inquirer.

All that vanished before the end of the 1950s. He died alone in a boarding house in Cambridge after doing his best for close to a decade to avoid being found by his friends. Nothing of his work was left. But beyond question his influence shaped much of the thought of the laboratory and the approach to physiology from a philosophical view.

See also

-- Jerome Lettvin


McCulloch, W., and W. Pitts. (1943). A logical calculus of the ideas immanent in nervous activity. Bulletin of Mathematical Biophysics 5:115-133. Reprinted in W. S. McCulloch (1965/1988), Embodiments of Mind. Cambridge, MA: MIT Press.

Pitts, W., and W. McCulloch. (1947). On how we know universals: The perception of auditory and visual forms. Bulletin of Mathematical Biophysics 9:127-147. Reprinted in W. S. McCulloch (1965/1988), Embodiments of Mind. Cambridge, MA: MIT Press.

Further Readings

Anderson, J. A. (1996). From discrete to continuous and back again. In R. Moreno-Diaz and J. Mira-Mira, Eds., Brain Processes, Theories and Models: An International Conference in Honor of W. S. McCulloch 25 Years After His Death. Cambridge, MA: MIT Press.

Cull, P. (1996). Neural nets: classical results and current problems. In R. Moreno-Diaz and J. Mira-Mira, Eds., Brain Processes, Theories and Models: An International Conference in Honor of W. S. McCulloch 25 Years After his Death. Cambridge, MA: MIT Press.

Howland, R., J. Y. Lettvin, W. S. McCulloch, W. Pitts, and P. D. Wall (1955). Reflex inhibition by dorsal root interaction. Journal of Neurophysiology 18:1-17. Reprinted in W. S. McCulloch (1965/1988), Embodiments of Mind. Cambridge, MA: MIT Press.

Lettvin, J. (1989). Introduction. In R. McCulloch, Ed., Collected Works of Warren S. McCulloch, vol. 1. Salinas, CA: Intersystems Publications.

Lettvin, J., H. Maturana, W. McCulloch, and W. Pitts. (1959). What the frog's eye tells the frog's brain. Proceedings of the IRE 47:1940-1959. Reprinted in W. S. McCulloch (1965/1988), Embodiments of Mind. Cambridge, MA: MIT Press.

Wall, P. D., W. S. McCulloch, J. Y. Lettvin, and W. H. Pitts. (1955). Effects of strychnine with special reference to spinal afferent fibres. Epilepsia Series 3, 4:29-40. Reprinted in W. S. McCulloch (1965/1988), Embodiments of Mind. Cambridge, MA: MIT Press.