"'The proof of the pudding" is actually closer to the original form of the proverb in question. The entire phrase is 'the proof of the pudding is in the eating,' meaning that the true value or quality of a thing can only be judged when it is put to use. ('Proof" in this context means 'the act of testing,' rather than our more common 'conclusive evidence' sense.) 'The proof of the pudding is in the eating' dates back to around 1600, and is more often heard in the United Kingdom than the U.S., probably because puddings of various kinds occupy a more prominent place on the dinner table there. 'The proof is in the pudding,' a fairly common mutation of the proverb, does make a certain amount of sense, i.e., that the final product, not the recipe, is what counts. But personally, I can't shake the feeling that 'the proof is in the pudding' would make an excellent last line for a Sherlock Holmes mystery." ~Evan Morris, The Word Detective.
"the proof of the pudding is in the eating - proof will be in the practical experience or demonstration (rather than what is claimed before or in theory) - in other words, you only know how good the pudding is when you actually eat it. The origin of the expression 'the proof of the pudding is in the eating' is four hundred years old: it is the work of Miguel de Cervantes (1547-1616) from his book Don Quixote de la Mancha (1605-1615). Modern usage commonly shortens and slightly alters the expression to 'the proof is in the pudding'. This is a wonderful example of the power and efficiency of metaphors - so few words used and yet so much meaning conveyed." ~ Alan Chapman, businessballs.com
"The usual rule in lexicography is that sayings progress towards corruption and decay, never the reverse." ~Michael Quinion, World Wide Words.
