The following is a message I sent to somebody over OkCupid today while I was bored. The user in question had the line, "I don't believe in fate" in the first few lines of their profile, while in their Religion section of their quick-facts was listed, "Christianity and somewhat serious about it." I decided to send them a message inquiring about this and, hopefully, I've made clear the why of it.
The person's response is in italics.
Title: So if there's no fate ...
Body: How does God know what his plan for you is?
I’m sure you have heard the fraise before “It will happen if it was meant to be.” Well I disagree, and that is why I highly discourage the whole idea of fate. Maybe I don’t like it for the simple reason that I lack control. Or the idea that I can’t prevent bad things from happening by the choices I make. I want to live my life the way I choose, not have it predestined for me. I believe people have to MAKE things happen if they want them too. They can’t just go on living saying it will happen if it was meant to be. If everyone said that where would we be today!? People need to take responsibility over your life and do what needs to be done. We can't wait for fait to chime in, if we do we’ll always be one step behind.
Yes, I do believe God can see into your future, but I also believe that you can change that future by the choices you make along the way. God gave us free will, if he made our destiny 100% then we'd have no free will.
In, say, six years, you will likely be in a substantially different place, both emotionally and physically, and perhaps spiritually as well. You might have children, a husband, a career that has nothing to do with your degree, and so on. These various things will happen to you because of either internal or external forces; that is to say, you will enact them intentionally, or items beyond your control will enact them for you. You may not wish to have children, for example, but you might end up being raped and be forced into an unwanted pregnancy. Bear with me, this is going somewhere.
In another six years, that unwanted child may require a journey to the clinic for one of various irrelevant reasons. However, maybe the week before you got into a car accident and, due to a series of unavailable loved ones, you may need to walk to the clinic with your child. On the way there, you might stub your toe, and it would hurt greatly. By virtue of any major Christian concept of God, He will know about this toe-stubbing, and will have known that it would occur before you were born - he would have known about it before Adam and Eve were ejected from the Garden of Eden.
This is the omniscient bit of Judaeo-Christian godhood.
In order for God to have known about this toe-stubbery this long ago, he would require knowledge of several things, which by definition he would have:
First, he would need to have an intimiate understanding of the many, many generations it would take to produce you and, ultimately, your child.
Next, he would require a detailed understanding of your life, including the events the produced your child and eventually forced your walk to the clinic that caused a toe-stubbing.
He would also need to know that there would be a rock, or stony outcropping, or raised sidewalk ledge, or any number of toe-stub-inflicting items in a very specific location; exactly where your toe would be on the day of the trip to the clinic.
In order for God to "see into [your] future," God would need absolute awareness of all of these things. To say that God can tell that you'll get married to boy X and have child Y, but not be able to see that you'll get a nasty toe-bruise on day Z is silly; to a supreme deity that has witnessed the birth and death of tens of billions of people, how is one event much different from another? You might say, "I decided to take my child to the clinic this day," and that would be true. You did decide that. However, if God knew you would be going to stub your toe in the exact moment you did, given the knowledge required to know that, can you really say that you were not predestined to do so?
Choose carefully here; to say that God doesn't know that you'll be stubbing your toe says also that God doesn't know everything, and if God doesn't know everything, then he isn't perfect. And an imperfect God, according to any number of major Christian theologians, is .. not God. To say that God is aware that you’ll be stubbing your toe on that day, as I’ve made the case for above, indicates a detailed knowledge about your life that is, essentially, the same thing as fate.