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Absolutely genuine or authentic; pure or untainted. A reference to the character Simon Pure in Susannah Centlivre's 1717 play A Bold Stroke for a Wife. The new leader is promising to bring simon-pure democratic principles back into the political discourse.
Absolutely genuine, quite authentic, as in That laboratory test was simon pure; none of the specimens was adulterated. This expression comes from the name of a character in a play, Susannah Centilivre's A Bold Stroke for a Wife (1717), who is the victim of an impersonation but turns up in the end and proves that he is "the real Simon Pure."