In John 12 Jesus had just prayed before the multitude, “Father, glorify Thy name.” “Then a voice came out of heaven: ‘I have both glorified it, and will glorify it again.’” (:28) What is interesting is the response of the multitude. Some obviously heard what God had said. “Others were saying, ‘an angel has spoken to Him.’” But others were saying “it had thundered.” (:29) It is notable that all the people were present for the same event, and actually heard the same thing; but some attributed it to God, others said that it was just thunder.
We see here that we human beings are not nearly as “objective” as we would like to think we are. Our response to God’s work reveals our hearts.
If we are inclined to believe in God, we will see His hand in a variety of situations, and credit Him for it. But if we are disinclined to believe, there is usually some other explanation which will suffice, be it “thunder” or whatever. And it seems to be in the plan of God that He often shows just enough of Himself for some to believe – but often also leaves His work just ambiguous enough that those who would prefer to doubt can find another explanation if they so choose.
This is not limited to instances like this one in John 12. We see the same thing in countless modern experiences as well. If a Christian goes to the doctor with a serious illness, and through prayer and treatment they recover, the Christian and those who are praying see God’s hand in it and give Him thanks. But those who would prefer to doubt will assert that God had nothing to do with it; it was just the medication. Again, God did enough for His people to give Him thanks, but also left it open for those who want to say, “it just thundered” to ignore Him if they will!
Blaise Pascal said it well: “In faith there is enough light for those who want to believe and enough shadows to blind those who don’t.”
In the end, our response to what we see happening around us is often less than an objective observation about certain events. It is more like a judgment which reveals something important about US – whether we will choose to believe or not. Will we by faith hear the voice, and see the work of God? Or like many in the crowd that day in John 12, we will say that it just thundered?
shawnethomas 
Two years ago, around Christmas my cat disappeared. As the days wore on I became more doubtful that he would ever come back. But on a really cold night a week later, as I bought gas at the local 7-11, it occurred to me: why not pray for a miracle? It was possible that my cat was still alive, somewhere. I knew God, if He was willing, was more than capable to grant my request and so with James 5:16 in mind, (“The prayer of a righteous person has great power as it is working”) I prayed often for Rascal’s return, making myself wiling to accept whichever way God would answer.. About a week later, I thought I heard a “meow” on my patio and there was my cat! He was a little thinner but in otherwise good shape. He had been gone for nearly two weeks. Some may say that he would have come back anyway and that is true. But I feel strongly in my heart that God had graciously answered my prayers. And not only that, this process taught me valuable and practical lessons about prayer through my experience.. Thunder? I think not.