Putnam's Twin Earth

Putnam's Twin Earth thought experiment illustrates that meaning isn’t solely determined by internal thoughts but also depends on external factors. Imagine Twin Earth is identical to ours, but the substance called "water" there is a different chemical (XYZ). When Twin Earthers say "water," they refer to XYZ, not H₂O, even though internally they think of water the same way we do. This shows that words get their meaning partly from the external environment and the actual substances in the world, emphasizing that language and understanding are grounded in real-world contexts beyond mere internal thought.