more from Gabriel M.A. Segal

Single Idea 3110

[catalogued under 18. Thought / C. Content / 5. Twin Earth]

Full Idea

Humans are largely made of H2O, so there could be no twin on Twin Earth, and (as Kuhn noted) nothing with a significantly different structure from H2O could be macroscopically very like water (but topaz and citrine will do).

Gist of Idea

Humans are made of H2O, so 'twins' aren't actually feasible


Gabriel M.A. Segal (A Slim Book about Narrow Content [2000], 2.1)

Book Reference

Segal,Gabriel M.A.: 'A Slim Book about Narrow Content' [MIT 2000], p.24

A Reaction

A small point, but one that appeals to essentialists like me (see under Natural Theory/Laws of Nature). We can't learn much metaphysics from impossible examples.