Out of curiosity, as I do not know enough details:
1. Alice owns one BTC
2. Bob owns one BTC
3. Both send their BTC to Charlie
4. Charlie sends one BTC to David
Question: Is there unambiguous way to define whether David got the BTC originally owned by Alice or the one owned by Bob? If yes, how? If no, doesn't that mean that there exist no specific bitcoins anywhere?
1. Alice owns one BTC
2. Bob owns one BTC
3. Both send their BTC to Charlie
4. Charlie sends one BTC to David
Question: Is there unambiguous way to define whether David got the BTC originally owned by Alice or the one owned by Bob? If yes, how? If no, doesn't that mean that there exist no specific bitcoins anywhere?