Where is the choice when you have a single course of action that must be performed? That's determinism, what is done must be done.
Like you say, what is done must be done. There, in the restaurant, choosing must be done. Choosing cannot be avoided. There is no deviation that can get you around the choosing. There is no alternative to choosing. Choosing happens because it must happen, specifically at that place and at that time.
You keep asking "where is the choice" when the choosing is happening right there in front of you. There is the menu, a list of alternate possibilities from which we select the single dinner that we will order. Do you need to consult the dictionary again?
Moving from the restaurant to the traffic example, we find we have a standard intersection of two roads. And here we find there are three things that I can choose to do. I can turn left, I can turn right, and I can drive straight ahead. Even though I will only choose to turn left to get where I'm going today, I still have the ability to turn right or go straight.
By saying ''there are three things that I can choose to do'' you are contradicting determinism, which has only one thing you can do in any given instance. In this instance: turn left.
In this instance I WILL turn left, even though I CAN turn right and I CAN drive straight.
What I CAN do at that intersection remains constant no matter what I WILL do.
Determinism tells us what I WILL do. But what I CAN do is determined by the physical arrangement of the two roads and my ability to drive a car.
In this instance you have no other options.
An option is something that I CAN do. My options are not limited by what I WILL do in this instance. Today I will turn left. Tomorrow I WILL turn right to go somewhere else. But on EVERY DAY I will have the same 3 options. There will ALWAYS be 3 options at that intersection, not just for me, but for every other driver as well.
Each driver has only one 'option,' this one must turn right, that one must go straight, that one must do a U turn because he got a call from his wife about an emergency.....each their own action, all possible actions are taken by different drivers, none has alternatives.
Each driver will have the same three options at that intersection. If a driver MUST turn right, then he WILL turn right. If another MUST do a U turn because he got a call from his wife about an emergency, then he WILL make a U turn.
Each WILL do their own action, according to their own goals and reasons, as they MUST. And each WILL still have the same 3 options, because they MUST have them at that point in time, due to the construction of the intersection.
Again, options that are generally available doesn't mean that multiple actions are available to everyone at any given time.
BUT THEY ARE! There's the intersection. There we are in the car looking at that intersection. (1) We CAN turn left. (2) We CAN turn right. And (3) we CAN go straight ahead. There are THREE realizable possibilities. ONE of them WILL be realized and the other TWO WILL NOT be realized in this instance, but they COULD HAVE been realized IF we had chosen to. And that is what REALIZ-ABLE means, that we were ABLE to realize them IF we had chosen to.
Determinism only permits one action at any given time. That action is different for different people/different states, one driver does x, the other does y.
With each driver, only one of the three possible actions WILL be taken. So, determinism is satisfied.
But in the moment of action, the one doing x can only do x, and one doing y can only do y.
At the moment of action there is only one thing that each driver WILL do, but three things that each driver CAN do. Determinism guarantees the three CAN's as much as it guarantees the single WILL. Because it was causally necessary from any prior point in time that the intersection would be designed to enable every driver to go left, right, and straight.
Countless different people doing different things, yet each only has one realizable action in the instance of acting; that which is determined. Multiple options do not exist at any given moment. Whatever happens, must happen.
How does each person discover what their one realizable action is without the notion of multiple options? For example, if I CAN only turn left at that intersection, then how will I ever reach any location on the right? There must be some rational mechanism that allows me to believe that I CAN turn right at that intersection. If not, then I must always turn left.