Just as there are precious few actual scientific experiments in psychology capable of giving a straight yes-or-no answer to a real question, there is not much in philosophy or metaphysics that can be similarly tested. I recently met with an instance.
You may have encountered this instance in a New Age context called "The Secret," or "The Law of Attraction," or other names I haven't heard, being a novice. The basic idea--forgive me, believers--is that what you think, visualize, or otherwise make real in your internal life, you will attract from the Universe and thus experience. So if you consistently imagine yourself rolling in money, you will become rich (if you are not already rich). This idea is not new.
The clause that arrested me was expressed by one friend ( no doubt quoting): The Universe doesn't hear "not." Thus if you constantly obsess, "No, I will not, not, not get cancer like my mother did," guess what?
I find this claim fascinating. It raises two distinct questions:
a) How to prove or disprove--in the sense of physical scince?
b) If so, why?