The very fact that non-believers want to know why God does, or allows, things to happen, tells us that they could accept God if they just could understand Him. I have sad news for them; Christians don't always know why God allows bad things to happen. All we really know in our hearts is that He always works what we see as a tragedy, into something good (Rom. 8:28). Notice that the verse says, to those who love Him. I have always thought that it meant He took bad situations, and made the result good because genuine born-again Christians love Him. I am beginning to think it has more to do with the Spirit in us, causing us to recognize the situation in light of the "big picture." The Holocaust is a perfect example: God allowed His people to suffer so terribly, that the world's conscience would move them to provide Israel with a homeland. Israel must possess the land of promise in order for Antichrist to reveal himself by desecrating their new Temple (Dan. 9:26; Matt. 24:15).
Of course, the natural response to that statement is, "All that may somehow be good for Christians, but what about the Jewish men, women, and children who were killed? How did it all work out for good to them?" I believer the answer is found in the statement, "And so all Israel shall be saved...." (Rom. 11:26). The previous verse explains that Israel's blindness to the truth of Jesus, was God's way of revealing His gift of salvation to all men (Rom. 10:9-13). Jesus had to be rejected by Israel in order that the entire human race could learn of His love through the death, burial, and resurrection of His Son (Jn. 1:11-12; 3:16; 14:6). In order for man and angels to comprehend the awesomeness of God's love, Jesus died (Jn. 17:23; 1 Cor. 4:9; 1 Tim. 3:16; 1 Pet. 1:12)!
Throughout the Old Testament, God tells man that He does things, and prevents those who are evil from doing things, so that all of mankind would understand that He is the LORD. The Bible is a declaration of God's sovereignty and love for His creation. His revelation of Himself is found in the Law (Ex. 6:7; 7:5; 14:18; 16:6; 29:46; etc.), the Prophets (1 Sam. 17:49; Isa. 49:26; Joel 2:27; Zech. 2:9; and in Ezekiel over fifty times), and the Writings (Ps. 46:10). All that God does, and all that He allows to happen, serve to reveal Him as our Creator, and Redeemer. God wants man to know Him for what He is: Love (1 Jn. 4:8, 16)!
Apart from the Bible, man cannot know God. Our minds are incapable of comprehending Him (Job. 5:9; Ps. 145:3; Prov. 25:3; Rom. 11:33; Eph. 3:8). That is why man has made other men gods (Buddhism, Confucianism, Shintoism, Zoroastrianism, etc.), and worship created things such as the Sun, Earth, "Mother Nature," and man made idols. It is the Bible that reveals God's love, His will, and the answers to every question that begins with "why." All things, natural laws, and the events of history can be understood because the Word of God tells us God is our Creator, and He works all things out for good, so that we may know Him, and most of all, trust Him. He has proven beyond a doubt that He is trustworthy. Amen.