Reagan:  "Trust but verify!"   That came out during the US/USSR anti-missile arguments--from the Russians!

"Trust, but verify is a form of advice given which recommends that while a source of information might be considered reliable, one should perform additional research to verify that such information is accurate, or trustworthy. The original Russian proverb is a short rhyme which states, Доверяй, но проверяй (doveryai, no proveryai)."

It's also a principle in scientific inquiry to not just believe what you want to believe, but produce measureable, quantifiable, results capable of being independently replicated by others.