Molyneux's problem

Molyneux's problem is a thought experiment in philosophy concerning immediate recovery from blindness. It was first formulated by William Molyneux, and notably referred to in John Locke's An Essay Concerning Human Understanding (1689). The problem can be stated in brief, "if a man born blind can feel the differences between shapes such as spheres and cubes, could he, if given the ability to see, distinguish those objects by sight alone, in reference to the tactile schemata he already possessed?"

The question was originally posed to Locke by philosopher William Molyneux, whose wife was blind. It is known from the report of it in Locke's Essay Concerning Human Understanding, which is reproduced here:

A similar problem was also addressed earlier in the 12th century by Ibn Tufail (Abubacer), in his philosophical novel, Hayy ibn Yaqdhan (Philosophus Autodidactus). This version focused on colors rather than shapes, and gave the opposite solution:

In 1709, in §95 of An Essay Towards a New Theory of Vision, George Berkeley also concluded that there was no necessary connection between a tactile world and a sight world—that a connection between them could be established only on the basis of experience.

Leibniz (German philosopher, 1646–1716) also discussed this problem, but derived a different answer. He suggested that the two sets of experience have one element in common, that is, extension. Hence it is possible to infer from one type of idea to another.

In 1749, Denis Diderot wrote Letter on the blind for the benefit of those who see as a criticism of our knowledge of ultimate reality.

One reason that Molyneux's Problem could be posed in the first place is the extreme dearth of human subjects who gain vision after extended congenital blindness. In 1971, Alberto Valvo estimated that fewer than twenty cases have been known in the last 1000 years.

In 2003, Pawan Sinha, a professor at the Massachusetts Institute of Technology, set up a program in the framework of the Project Prakash and eventually had the opportunity to find five individuals who satisfied the requirements for an experiment aimed at answering Molyneux's question experimentally. Prior to treatment, the subjects (aged 8 to 17) were only able to discriminate between light and dark, with two of them also being able to determine the direction of a bright light. The surgical treatments took place between 2007 and 2010, and quickly brought the relevant subject from total congenital blindness to fully seeing. A carefully designed test was submitted to each subject within the next 48 hours. Based on its result, the experimenters concluded that the answer to Molyneux's problem is, in short, "no". Although after restoration of sight, the subjects could distinguish between objects visually almost as effectively as they would do by touch alone, they were unable to form the connection between an object perceived using the two different senses. The correlation was barely better than if the subjects had guessed. They had no innate ability to transfer their tactile shape knowledge to the visual domain. However, the experimenters could test three of the five subjects on later dates (5 days, 7 days, and 5 months after, respectively) and found that the performance in the touch-to-vision case improved significantly, reaching 80–90%.

Ostrovsky, et al., in 2006, studied a woman who gained sight at the age of 12 when she underwent surgery for dense bilateral congenital cataracts. They report that the subject could recognize family members by sight six months after surgery, but took up to a year to recognize most household objects purely by sight.

Regarding Molyneux's problem, the authors Asif A. Ghazanfar & Hjalmar K. Turesson (2008) have recently noted that there are not separate brain processes for motor outputs and individual sensory modalities, but rather that the brain uses all available context-specific information to act – that is, all information associated with a specific action. They suggest that this makes Molyneux's problem into an ill-posed question, from a neuroscientific perspective, since Molyneux does not suggest an action to be done with the cube and the globe.

In 2024, chickens were reared from incubation and hatching in total darkness, then exposed in said darkness to objects of either smooth or bumpy textures for 24 hours. They were then tested on visual recognition of the objects as they first experienced light. Upon first sight, chicks that touched the smooth objects approached the smooth objects much more often than chicks that touched bumpy objects did.

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• Taine, Hippolyte (1870). De l'intelligence. Paris.
• Degenaar, Marjolein (1996). Molyneux's Problem: Three Centuries of Discussion on the Perception of Forms. International Archives of the History of Ideas / Archives Internationales d'Histoire des Idées. Vol. 147. Kluwer Academic Publishers. doi:10.1007/978-0-585-28424-8. ISBN 978-0-585-28424-8.

• "Molyneux's Problem" entry in the Stanford Encyclopedia of Philosophy
• "Molyneux's Question". Internet Encyclopedia of Philosophy.