I have been struck by a couple of conversations in the past week regarding this question.
Perhaps you have dealt with this in your life, particularly when facing the trials and tribulations of life.
More than a few times, I hear someone wrestling with troublesome events by saying, "There is a reason for this. God has a reason for this. I may not know what it is, but I know He has a reason for this."
I think I understand why people say such things. I think it has something to do with a philosophical conundrum which has defied human reason, and, in fact, has become an argument that some use to say God does not exist. The conundrum follows:
If God is all powerful and all good, then He has the ability to abolish evil. If He does not abolish evil, then He is not all good. If He cannot abolish evil, then He is not all powerful.
In order to preserve the sovereignty and goodness of God, many, including myself, have said, "We must give allowance that we cannot see the big picture and that God has a reason for allowing certain things to happen as they do." --Everything has a reason.
I think we must address a couple of points--first the idea of God's power.
I believe God is all powerful in the sense that there is no entity which has greater power than God; however, I believe God gave up some of His own power. That may sound blasphemous, but hear me out.
God gave to creation free will. God does not manipulate our hearts and minds to force us to act in a certain fashion. If He did, we would simply be robots, mere puppets on a string. (I love John Lennox's comment regarding this. Paraphrasing: If I went home to a robot wife and hit a button on the computer which made her say, "I love you," it wouldn't be too particularly satisfying." God forcing us to love and obey Him would have the same effect.)
Some have argued: well, why doesn't God limit our ability to perform evil. Hello! Ever hear of a conscience? But, I digress.
Because we have free will, God may know our chosen course of action, but He does not always intervene. Intervention at all times would mean that we would never learn any lessons (pain is a great teacher), and we would simply become objects of God's control once again--kind of like those robotic toys running around in those enclosed areas in the mall. They can go all over the place and run into things, but they are cordoned off in a particular area and are still toys.
So, then why does it seem like after some time, thought, and reflection, it looks like many things happen for a reason?
I submit to you, that most of God's intervention takes place AFTER tumultuous events occur. God's intervention occurs as He begins working to make good come out of the things we suffer--either by our own free will or because of the freedom of nature.
As God works in our lives to bring transformation, we begin to see something unfold which has brought us to a new level of understanding, a new level of love, a new level of compassion, or what have you. God did not cause evil to befall us; He didn't intervene because of the freedom bestowed to His creation; yet, He began working to transform that evil into something good.
Sometimes, we can see this almost instantaneously. Sometimes it takes years, even decades, but when we finally see it, we have a "reason" for what happened. However, that reason wasn't there before the event, it only came after God's intervention and healing work in the world.
Do all things happen for a reason? No.
Can God work to make it seem that way? Yes, and I am convinced He does.