You're right. If you hang up seashells in your house and nothing bad ever happens is that because the seashells worked or because nothing bad was ever going to happen to begin with?

If I give a customer silver bells to keep bad dreams away and it doesn't work is it because they didn't believe it would or because the bells simply don't work?

When you think about it like that it's truthfully hard to say. What is magic and what is coincidence?

My answer to that would be to say that nothing in this world is a coincidence. Everything is Hitsuzen. Everything in the world is a driving force of some kind. There is magic everywhere. And if you stopped having dreams because of silver bells and if your home was kept safe because of sea shells then that is what was meant to be. These driving forces allowed that to happen.

But that, of course, is my belief. That is how I see the world and how I know it to work. Someone else's vision may be different. You may very well need more concrete proof that these things are moving and working. And so you'd say that my seashells protecting your home are purely coincidence and you would argue an actual barrier would prove more efficient, more magical. And there's nothing wrong with that. That's simply your view of magic.