Dublin born Thomas Kingsmill Abbott (26 March 1829 – 18 December 1913) is probably best known for his translations of Kant’s ethical works published in 1873 which remained the standard English texts into the 1940s (Duddy, 2004). He had a wide range of scholarly interests, being professor various of Moral Philosophy, Greek and Hebrew in Trinity College Dublin. However his greatest philosophical contribution was made in his early career, where he disputed the theory of vision outlined by (fellow Trinity man) George Berkeley.
The roots of Berkeley’s theory are in Locke. Just before he introduces (William) Molyneaux’s Problem, in his Essay on Human Understanding (IX, 8) Locke states that “When we set before our eyes a round globe of any uniform colour […] it is certain that the idea thereby imprinted on our mind is of a flat circle”. The roundness we think we see, says Locke, is the effect of experience, which differentiates what we see: “…only a plane variously coloured, as is evident in painting.” He does not, however, claim we cannot tell that the sphere is at a distance.
William Molyneaux does claim this, however, in his Dioptrica Nova (1692, 113):
Distance of itself is not to be perceived. For it is a line (or a length) presented to our eye with its end toward us which must therefore be only a point, and that is invisible.
Berkeley expands these ideas in A Essay towards a New Theory of Vision (1709/1732), referenced previously in relation to the Moon Illusion. Berkeley agrees with Molyneaux that distance cannot be seen (II):