Progress, far from consisting in change, depends on retentiveness. When change is absolute there remains no being to improve and no direction is set for possible improvement: and when experience is not retained, as among savages, infancy is perpetual. Those who cannot remember the past are condemned to repeat it.

George Santayana (1863-1952) Spanish-American poet and philosopher [Jorge Agustín Nicolás Ruíz de Santayana y Borrás]

The Life of Reason or The Phases of Human Progress, Vol. 1, “Reason in Common Sense,” ch. 12 (1905-1906)
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Often given as "Those who do not remember the past ...." Quoted at the Auschwitz Holocaust Museum, via Polish, as: "The one who does not remember history is bound to live through it again."

Often misattributed to Winston Churchill, who paraphrased it in a Commons speech in 1948: "Those who fail to learn from history are condemned to repeat it."