Can you tell the difference between butter and "I can't believe it's not butter" ?
That is a complicated question.
You see, if you were to hand me a piece of toast with butter and a piece of toast with "I can't believe it's not butter" I would not be able to tell the difference. Taste, smell, visuals, feel, nothing would help.
Now, if you were to give me the aforementioned toast and ask me to decide which is which, that's when the work begins. After extensive lab tests including blood test, litmus test, wafting method, electrotherapy, and looking at what container each came from, I would be able to give an answer.