What is the subject of a magic trick?

Is it the topic of the story in the trick?

Do all magic tricks have a story?

Do they all have a topic?

What is the subject of The Cups and Balls?

Those are five big questions and we may need to look a little bit further away from the magic catalog to have good answers.

Sentences have subjects and verbs. Stories have antagonists and conflict. Essays and dialogs have topics.

All performances show a story to the audience - by theatrical convention of the curtain going up, the action and then the curtain going down.

Not sure who to address the cups and balls question as that's kind of like asking if water has a story. A cup of water on your table may have a story, as does the water in your fishtank - but that's not the same as "the story of water" itself.

Just my musings - others likely have better answers for you.

To answer most of your questions in general I will just put "Entertainment."

“Something or somebody is caused to pass mysteriously from one place or
condition to another. That is what invariably happens when a magical feat is
performed. We cannot do any single magical thing which that sentence does not broadly describe.” NM

What’s the story? A magical feat is no story at all! With no story there can be no subject and with no subject there is no depth which can be conveyed to the audience to make it interesting.

The magical feat is something performed by the magician but give that feat a story and now we are talking, we can then identify the subject and work on the depth of the subject and that is the important thing; The depth of the subject!

I.e.

In effect; A playing card mysteriously moves from one place to another. Nice magical effect but no story, no subject and as shallow as a puddle on a dry day. Now think of a subject, an interesting subject. Lets say for instance, money! Now fit a story about money to the trick. Then you have a subject to work with. Like, does money vanish when lost on the stock market or just move mysteriously from place to another etc etc.

Is that correct, does it make sense? Just my musings.