Molyneux's problem
Molyneux · reported in Locke's Essay · 1688
Imagine a man blind from birth who has learned to tell a cube from a sphere by touch: hands on them, he can say which is which. One day, through an operation, he gains his sight. The cube and the sphere are set before him, without his being able to touch them. Will he be able, by sight alone, to say which is the cube and which the sphere?
Will he recognize the shapes by sight alone, or is everything to be learned from the senses?
What it does in the debate
Objects to Rationalismattacks the position
If the ideas of shape were innate, the newly sighted man would recognize them at once by eye; that he must relearn them through a new sense argues against innatism, the core of rationalism.
- If reason carried innate ideas within it, geometry would be in us before any sensory experience, independent of the sense through which one learns it.
- Yet a man born blind who has learned by touch to tell a cube from a sphere, and who suddenly gains sight, would he recognize them by eye, without touching? Molyneux and Locke answer: no, he would first have to learn to see.
- If the ideas of shape were an innate stock that reason unfolds, he would recognize them at once through any sense; that he must relearn them shows they are forged in experience, sense by sense.
Therefore So ideas are not an innate treasure that reason unfolds, but something acquired through experience: the Molyneux case argues against innatism, and so against rationalism.