How can you tell if your benefit came from your chanting or was just spillover from someone else's?

Within the SGI, we were all started off on "Chant for whatever you want!" and weaned onto "This practice works!"

All right, so let's take a case in point - all green lights on your way to work.

"I was late to work, so I chanted, and somehow managed to get all green lights, so I was able to make it to work on time! Thank you, gohonzon! Thank you, Mystic Law! Thank you, President Ikeda!!"

Now let's suppose there were 4 other cars traveling down the same road near you (behind, in front, next to), and THEY all experienced the same all-green-light phenomenon. One is a Hindu; one is a Pentecostal; one is a Catholic; and one is a Muslim.

The Catholic: "Thank you, blessed Virgin Mary, for your lovingkindness in looking out for me on my way to work and intervening in our world with this miracle just for me!"

The Muslim: "Allah is certainly good and generous - look how he looks out for His people!"

The Pentecostal: "Blargafloopringblingochingozanzibarbuckbuckfrubbate! Thank you, Lord Jesus, for abrogating the laws of reality and modifying the world to fit MY needs."

The Hindu: "Thanks heaps, Vishnu!" (What do I know about Hindoos??)

So who was right? How can we check? Obviously, nobody knows. Each person credits this event to his particular external locus of power, facilitated by his own devout practice, and then regards the event as an affirmation that he is, indeed, practicing the one True religion!!

Of course, they are probably ALL entirely wrong - it was a random occurrence; such things happen occasionally; no gods required.