半信半疑

1. Origins, structure, and basic meaning

• Structure: 半信半疑 (はんしんはんぎ) is a nominal predicate for an uncertain attitude divided between belief and doubt.
• Basic usage: 半信半疑で話を聞く adverbially describes the attitude toward a friend’s story, while 半信半疑だったが predicates prior doubts despite which a method was tried.

2. Common pitfalls and similar expressions

• Adverbial stance and past predication
  • 半信半疑で attaches to the manner of listening, while 半信半疑だった closes the state in the past. The が in the second introduces contrast; the method was still tried.