Something does not have to be proveable to be true. The quote comes from a description of quantum physics, where by simply observing a particle you affect it. In that case, the quote would really be When you look at things, they change. That of course would be a much less interesting and insightful quote.

However, I do believe there is a large degree of validity to this quote when applying it to an individual and life's issues. Often a person's perspective on an issue directly relates to their actions, and therefore causes a certain type of reaction by whatever 3rd parties are involved. By changing that person's perspective, you change the reaction, and thus the situation. That is how I understood the quote. The author of the quote (you can find from a google search) I believe took this to a whole different level, I belive his book is called "the power of intention". At any rate, I personally think he took this theory a bit too far, based on what I gathered watching him on PBS for 15 minutes or so.

At any rate, clearly an interesting, and debatable, quote.