Pre-determination implies there is a plan for the Universe, a fixed route to get from the past to the future. In this type of Universe no accidents occur because they were all suposed to happen and although we think we are making choices we’re not, we’re just conforming to the plan.
In The Matrix amongst all the protagonist’s abilities he had the ability of foresight, this gift was only for events within the matrix and its machinery but not the real world. How does this apply to us?
In an enclosed environment if you know everything that effects an object and you know all the objects in an environment then you can predict the outcome. In an imaginary frictionless box you place a ball and give it a nudge the ball will bounce around and keep doing so. You can predict the bounces if you know what angle the ball was nudged at and thus route the path before it happens. Adding another ball just means that it’s more complicated, both paths have to be plot to the same duration and when they bounce the directions calculated. Its harder work but it is possible with enough time and thought.
The Matrix was a realtime occurring environment, so more events were occurring every second, but agents and thus the Matrix itself have limits so if you’ve got a faster processor (such as your brain) then you can run the same events faster and find the outcome sooner. However there are limitations in the Matrix and in the real world.
No-one can see beyond a choice they don’t understand, and I mean no-one.
What The Oracle is saying that you can only have foresight if you know what choices you (and the rest of the matrix) are going to make, if you don’t know then when running the ‘foresight version’ of the Matrix then you’ll reach an impasse and not know anything further. So for someone contending with the person that has the foresight the phrase “you’ve already made the choice, now you have to understand why you’ve made it” is quite scary because they know what you are going to do and why you did before you’ve had the choice present itself and searched all your past experiences for the answer.
Having a plan for the Universe means that it is possible to know what choices people will make before they make them so it is possible for us mortals to see into the future.