I've heard it commonly taught that God is omniscient or all knowing. I've also heard that he is the author of all creation. If God is all knowing then he knows the past, present, and future and "wrote" it all.

Since he knows the future and the choices we'll make, are our choices really our own? He claims to have given us free will, but since he has the future already, our decisions are already mapped out.

How is it possible to have both an all knowing God and free will?

Welcome to the forum!

As to the topic -- I have never seen any difficulty between God knowing all things, and free choice. So don't see why there would it be a problem?

In my studies, I have found that God not only knows what we will do, He also knows what each outcome would be IF we made a different choice.
In the Bible we see a lot of prophecies stating
-- if they choose to do this, then these things will happen
-- if they choose a different way, then these other things will happen.

Think of it this way --
Suppose you had a dream revealing exactly what a friend of yours will do, and the consequences of their actions would be bad.
Now you know exactly what that friend is going to do.
Would your knowing what they will do take away their free will?
Now, knowing your friend is about to make a bad choice, you'll probably try to persuade them to make a different choice? But in the end they make their own bad choice and suffer the consequences.

In a way, God is very much like that -- He knows what choices we will make, and yet He does His best (through the Holy Spirit, or through other people) to persuade us to make the right choice, but in the end we make our own free choice, His foreknowledge does not make the choice for us.
It is OUR choices that God knows -- it's not God's knowledge that makes the choices.

We, as humans have a tendency of trying to limit God .
But God is not only present in all time (past, present, future) -- He also operates in OUR time. In dealing with mankind He deals with us in OUR time in a very personal way.

In the dream scenario, whether or not I try to convince my friend to make the right choice doesn't matter. In the dream, they made the bad choice and since the dream is of the future, no amount of persuading is going to change their decision. Their choice is made before they make it. Its predetermined. If my attempts to convince them were successful, then the dream would have portrayed that. In real life, they would have made the right choice after I convinced them to.

When God gives us choices in life, He knows how we will respond. Our choice is already known so we are just following the script. Thus, free will is a construct of our imagination.

Knowing something does not predetermine it.
We know WWII happened, but our knowing it happened, did not predetermine it thus leaving the instigators of the war without choice -- they weren't just following the script, just because the people living in the future know it happened. They were writing the script, we just know it happened.

Neither does God, being able to see the future, predetermine the choices we make.
Our choices write the script.

The awesome thing is that God, even though knowing so many will make the wrong choices, keeps working with us, wooing, pleading with us to make the right choices.

He wants NONE to be lost, and has made full provision for all to have salvation, yet SO MANY refuse.

In the judgment, the sad truth will be clear that those who are lost, are lost because of their own choice.

Christ knew that Judas would choose to betray Him, but He still accepted Judas as one of the 12 disciples. Christ didn't interfere with his freedom of choice.

I'm not implying that God actively interferes with our free will. I'm implying that the choices we make have no value as choices since the answer is always already known.

Knowing something happened in the past is not the same as knowing the future. What I hear ashes saying is that if God knows all of the final outcomes, our perception of our "free choice" is pointless, because the end is actually already pre-determined.

Second point, God knowing something and Humans knowing something are not the same, either. God knowing it may in fact pre-determine it.

Welcome to the forum, ashes. If you're looking for answers and open exchange of ideas, this is maybe not the place. If you're a dyed-in-the-wool Adventist who can't think outside the box you'll fit right in.

The answer may already be known to God, but it isn't known to any of us.

Our choices, even though known to God, remains our choices, do they not?

Our past, present, and future choices, even though they are all known to God, still have both value and consequences.

Think of the consequence of the choice made by both Eve and Adam that resulted in their being banished from the Garden of Eden.

Nadi and Ashes
Yes, it's true, God does predetermine the outcome. His promises are sure. The future is in HIS hands and we can depend upon Him to fulfil it just as prophecy foretells.

But this does not negate the value of our choices.
We -- in our moment in time -- are free to make the choices and those choices make all the difference in our eternal future.

Yes, God has predetermined from the beginning that
those who put their lives in His hands, and trust in Him are His children by adoption, to the praise of the glory of Christ's grace, wherein he has made us accepted in the beloved.

It is also predetermined that those who reject Christ and follow the evil prince that works in the children of disobedience, will not inherit the eternal kingdom.

Indeed there is much that is predetermined by God -- He predetermined to let sin run its course, as an object lesson to the whole universe as to what the abject evil of living contrary to His laws is actually like.

Indeed, it is a great comfort to know that God KNOWS the future and will do all He has promised.

Yet -- this does not negate the value of our choices.
Rather it INCREASES the urgency and need to make the right choice!

It is OUR individual choice to choose to trust and follow Christ, Who will make us accepted in the beloved and place us with Himself on the winning team that leads to eternal, beautiful life. OR choose to follow the prince that works in the children of disobedience, and even if it might seem to have temporal advantages, the predetermined end of that team is misery and eternal death.

That's where our freedom of choice is extremely important!
We choose which team we are going play on -- that is our free choice ==
The end each team faces is predetermined. But which team we want to play on - is OUR CHOICE.
God knows what choice we will FREELY make. But it's still our FREE choice.

Deut 30:19 "I have set before you life and death, blessing and cursing: therefore choose life, that both you and your offspring may live:
Joshua 24:15 choose you this day whom ye will serve; ...as for me and my house, we will serve the LORD.
Ezek. 33:11 As]I live, saith the Lord GOD, I have no pleasure in the death of the wicked; but that the wicked turn from his way and live: turn ye, turn ye from your evil ways; for why will ye die,

All of which may, or may not, be true. However, it fails to address the question in the OP. As such it is simply another of your attempts at distraction because you fail to understand the point under discussion.