Have you ever heard this argument: “If God is all-knowing, then He knows about all evils. If He is all powerful, then He could stop all evils. If He is all-good, then He would stop all evils. But evil exists, therefore, God does not exist”?
Yet, this outrage against evil implies a standard of goodness and justice that humans seek but cannot find without God. In other words, if God does not exist, an objective standard of goodness and justice does not exist.
Now, evil is not the result of God, but the result of humans abusing the free will God gave us.
Free will allows us to choose love over hate, truth over lies, God over self. Without free will, we would be like non-rational animals operating on pure instinct or robots operating by predetermining codes.
Ultimately, God gives us free will because He is Free Will, and He chose to make us in His image and likeness. However, a difference exists between a finite creature who can choose to reject what is good and perfect, and the Perfect Infinity who cannot fail to be good.
Understanding Why Evil Is In the World
“To help understand creation and the Fall, the image of three iron rings suspended from a magnet is helpful. The magnet symbolizes God; the first ring, the soul; the middle ring, the body; and the bottom ring, nature. As long as the soul stays in touch with God, the magnetic life keeps flowing through the whole chain, from divine life to soul life, body life, and nature life. The three rings stay harmonized, united, magnetized.
But when the soul freely declares its independence from God, when the first iron ring separates from the magnet, the inevitable consequence is that the whole chain of rings is demagnetized and falls apart. When the soul is separated from God, the body is separated from the soul-that is, it dies-and also from nature-that is, it suffers. For the soul’s authority over the body is a delegated authority, as is humanity’s authority over nature. When God the delegator is rejected, so is the authority he delegated. If you rebel against the king, his ministers will no longer serve you. Thus, both suffering and sin are traced to man, not God.”
Now, in our fallen state, the soul’s acquisition of grace does not reconnect all the rings. Rather, the rings remain separated, but grace allows us to bring them ever closer to the magnet. The rings will not reconnect with each other and with God until the Second Coming, when God gives us our glorified bodies and makes the heavens and the earth new.
 Peter Kreeft; Ronald K. Tacelli. Pocket Handbook of Christian Apologetics (The IVP Pocket Reference Series) (Kindle Locations 396-400). Kindle Edition.