doubting Thomas

 
Pronunciation: /daʊtɪŋˈtɒməs/

noun

  • a person who is sceptical and refuses to believe something without proof: I was a real doubting Thomas. I didn’t believe the stuff would work those doubting Thomases still can’t figure out how the show became a hit

Origin:

early 17th century: with biblical allusion to the apostle Thomas (John 20:24–29)