The phrase "Trust, but verify" is often attributed to former U.S. President Ronald Reagan. He popularized this phrase during his negotiations with the Soviet Union regarding arms control agreements in the 1980s.

Reagan first used the phrase during his speech at the signing of the Intermediate-Range Nuclear Forces Treaty (INF) in 1987. The INF Treaty aimed to eliminate intermediate-range and shorter-range missiles from Europe. During the speech, Reagan stated, "The phrase 'trust but verify' was a Russian proverb that I learned from Mr. Gorbachev, and I think it's appropriate that we use it in this treaty."

The phrase emphasizes the importance of maintaining a cautious approach when dealing with agreements and negotiations. While trust is an essential element in any relationship, Reagan stressed the need to verify and ensure that the agreed-upon terms are being honored.

The idea behind "trust, but verify" is that trust should not be blind or unconditional. It is crucial to have mechanisms in place to verify that the commitments made by the other party are being fulfilled. This approach promotes transparency, accountability, and ensures that both parties are acting in good faith.

The phrase has since become a widely used principle in various contexts beyond arms control. It has been applied in business negotiations, international diplomacy, and even in personal relationships. The underlying concept is to strike a balance between trust and skepticism, recognizing the importance of verifying information or actions to avoid potential pitfalls.

While Reagan popularized the phrase, it is worth noting that he attributed it to a Russian proverb. However, there is no concrete evidence to support that the exact phrase was a well-known Russian proverb before Reagan's usage. Nonetheless, Reagan's use of the phrase during the INF Treaty signing ceremony and subsequent speeches made it synonymous with his presidency and his approach to negotiations.