This question came up in the Online 10-day Retreat Nov 3, 2020, guided by Delson Armstrong. Day 1 was part of a daily 30-minute discussion on the suttas, the Dhamma talk and reflections.
Slightly edited to improve readability
I look at Formations as carriers of Kamma, meaning they are the ones that provide the kammic impulse. You will see this later on as we progress with the retreat, that in relation to the level of Contact, is where you have all the old Kamma.
There is the Feeling that arises. What you do with that Feeling will then determine whether new Kamma is created or not. Whatever we are experiencing up to the level of Contact and Feeling, is old Kamma. It’s the effects of choices we made in past lives, whether it’s just a split second ago or eons ago. Whatever we are experiencing in the way of our six senses, and in the way of our experience with the mind and body, is all the inherited effects of Kamma. So, I would shift the perspective in looking at Formations from that angle. And then see that whatever we experience, is a result of our choices. That is why I began with Effective Choice.
Going back to the question; it’s a matter of the Formations deciding in that moment, because they were conditioned by a previous choice we made. They are not deterministic, they are rather conditioned by our choices we made in the past. Because of that, we can change the Formations. We can strengthen certain Formations, based on choices we make in this present moment, or we can weaken them.
That is why the Noble Eightfold Path is called the cessation of Kamma. Because when the Formation arises, as the carrier of Kamma, it then is activated through the process of Dependent Origination, to the level of Contact and Feeling. At that point you have the old kamma, which is the effects of choices you made previously. Once you have this Feeling, it’s how you perceive it, how you take it. Is it through Wise Perception and letting go of any attachment and craving to that Feeling right there and then; that will determine the next set of Formations, which will allow you to continuously let go in the next set of choices.
But the more you attach a sense of self, the more you crave that Feeling by attaching a sense of self, the more you are determining, from your present choices, the future Formations which will be strengthened. Those will then determine the choices you make, which are tending more towards creating more Craving for yourself.
Formations are always conditioned by choices. And choices, in that regard, are conditioned by old Formations.