Last week was about God's omnipotence. This week we move on to omniscience. Here's the developing map.
God knows every possible thing to know. He knows every possible thing that could happen in this universe.
That doesn't quite get us to "all knowing" yet. That's the next article. God's "omniscience" is the Christian belief that God knows everything, both possible and actual.
We know that God knows everything that is possible because he created the world out of nothing. Creating the world out of nothing--including the emptiness--is not like when you or I make something in the kitchen or when some architect designs things. We not only have inherited the materials from the creation but we have inherited the laws of physics and chemistry that set the boundaries for what we can create and how materials interact with one another.
Not so for God. When God created the universe out of nothing, he created the laws of physics and chemistry. He created the boundaries for what materials can and cannot do. There is nothing that exists in this universe that God did not completely and utterly design. He therefore knows everything it is possible to know and even more.
Often when we think about God, we mistakenly assume that his knowledge is similar to the way we know things. For example, for us, there is a difference between knowing things with your head and knowing things experientially. But since God created the universe out of nothing, he created any experience you could possibly have.
This is a significant point. God created even experiences like suffering and sinning. The humanity of Jesus learned obedience and suffering on the cross (Heb. 5:8), but God the Father and God the Spirit did not learn anything on the cross. God created the possibility of experiencing suffering. God created the possibility of learning obedience.
Similarly, God created Satan and the angels who fell from heaven. God created the possibility that Satan would fall. God created the possibility that Adam would sin. Later, we will look at the question of how a good God could create the possibility of evil. For now, however, we need to point out that God must know what it feels like to sin because God created this possibility out of nothing. He designed the universe to have this possible experience in it.
If a person believes that God has built some freedom into the creation, which I do, then the causes and effects of the universe can play themselves out in more than one possible way. There become, as it were, multiple "possible universes." I believe that God has made it possible for human beings to make more than one possible choice, despite the causes working on them. It may even be possible on the subatomic level that God has put some indeterminacy into the creation itself. 
Because God created the universe, he at the very least knows every possible eventuality. He knows how the universe can bend because he created all those possibilities. This knowledge is sometimes called "middle knowledge."  He knows every possible world that could exist depending on the choices people make.
There are two other forms of God's knowledge that are sometimes discussed. Certainly God knows how he will freely act in this world, his "free knowledge." However, it is important to realize that what are sometimes called "necessary truths" (e.g., 2 + 2 = 4) are also products of God's creation. Some Christian philosophers inadvertently blur God with the creation by forgetting that, when he created the universe out of nothing, he freely created all the possible axioms, postulates, and consequent theorems of math and other so called necessary truths. Necessary truths thus exist as an act of God's free will just like all other truths.
An argument for the existence of God that fits with his knowledge of the world is the so called "argument from design" or "teleological" argument for God's existence. The idea is that the complexity of the universe, its design, suggests that it had an intelligent designer.
The argument was classically set forth in the 1700s by William Paley along in the lines of a clockmaker.  The idea is that when you find a clock, you assume there was a clockmaker that made it. So Paley argued that something as complex as the universe must have had a universe maker.
The theory of evolution at the very least made it more difficult to make this argument. Nevertheless, there is more to the design of the universe than the specific complexity of life. There are the rules of the universe itself, the laws of physics and chemistry, for example.  Whether you find this argument convincing or not as a proof, Christians have no problem seeing the order and complexity of the universe as a reflection of God's omniscience.
Next Sunday, G6. God knows every actual thing to know.
 The current consensus in the field of quantum physics is that there is a fundamental indeterminacy to the universe on the subatomic level. The beginnings of this trajectory in physics trace back to the "uncertainty principle" of Werner Heisenberg first set out in 1927.
 The idea of middle knowledge can fit both with those who believe God determines all human choices and those who believe God gives humans some freedom in their choices.
 In a work called, Natural Theology.
 Richard Swinburne has made this argument in The Existence of God, 2nd ed. (Oxford: Oxford University, 2004).