If events do not logically flow from one to the other, than there is only chaos. That is self-evident. If people didn't have a reason to plow off cliffs, and if plowing off a cliff didn't necessarily result in falling off of it, then 1 might as well equal 2, or 16, or 0, or orange, or the mere concept of applebees.
The unsettling part of predestination is that it suggests that we don't have free will- but I disagree. Free will is the ability to determine our actions. If we do not rationally respond to the events that surround us, then we are reacting randomly. What is less like "free will"- totally random action, or reasonable action and reaction based on internal and external events?
Predestination is thus only a problem if we were somehow able to predict the future- a concept that (aside from little mathematical trickery on the quantum scale) seems to be impossible, with time machines or with computer simulations. Even if we did know all the physical laws- which we don't- and were able to measure the position of every smallest constituent particle in a relevant area- which we can't- then we would not be able to simulate that area at any reasonable rate- the simulation would be slower than real time, even with magical computers that were made of individual atoms for logic gates and were the size of planets.
More importantly, to 100% accurately simulate one particle, you must simulate all the particles that interact with it, 100% accurately. Since particle interact with other particles, in order to simulate an area one cubic inch in diameter for one second, you must simulate the action of all particles within a sphere one light-second wide... plus (if this cube is on earth), the continuing forces such as gravity and incoming radiation from bodies outside of that area, like the moon, sun, and other planets. They have small effects, but quantum noise is a perfect medium for chaos theory.
To predict the next word I say 100% accurately, you'd need to know what a butterfly ate six weeks ago in a greenhouse in china, which of electron was emitted from a hydrogen atom near the sun's surface 20 minutes ago, and weather or not a uranium atom at near-0k in the Oort cloud has decayed over the last three years... assuming you had a tool to detect all of these events down to the smallest physical level, a computer with enough storage space, and a total ruleset for the universe.
Of course, since you know how english works and the nature of context, then you yourself can probably predict the next
in a sentance with something like 50-60% confidence in general and somewhere between 10-99% depending on the situation. Which makes you better at predicting my actions than the best supercomputers in the world are at predicting the weather. Does that mean that I (or, for that matter, you) lack free will? No. The ability to predict things with 99.999999999% confidence, or 20%, is effectively the same.
This is an old debate, but one that I think science is slowly resolving in the most satisfying possible way- showing us that we are part of a fantastically complex universe that shapes us as we shape it, a universe we can learn about without ever running out of surprises.
Caral Sagan said that we are the cosmos, knowing itself. I cannot make my own arguments half as reassuring or inspiring.