"What Is Truth" is a single by American country music artist Johnny Cash released in February 1970. Generally viewed as a protest song, a rarity in country music at the time, the simple criticism of the Vietnam War, and war in general, as well as the stereotypical view of many politically liberal hippies made the song a major crossover hit. The song peaked at number 3 on the Billboard Hot Country Singles. It also became Cash's 12th Top 40 single on the Hot 100 chart, peaking at number 19, and his 2nd Top 10 single on the Adult Contemporary chart, peaking at Number 4. It also reached number 1 on the RPM Country Tracks chart in Canada.

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