I was using nondeterminism as “not determinism”, “not able to be determined”; indeterminism. But in the analogy of an algorithm, supposing your algorithm contained steps which waited on a human being to enter a value at his or her discretion, such an algorithm is nondeterministic (within the realm of computer science; a person analyzing the algorithm in isolation could not predict the output).
Like so with libertarian free will, where physics stands in for the algorithm. It is hypothesized, by libertarian philosophers, that the physical universe is not deterministic. It is also assumed that free agents (souls) external to the physical universe step in and interact with the physical universe (mind-body dualism), usually restricted to abide by (indeterminate) physical laws. By what exact mechanism the free agents decide, it is impossible to tell based on physical evidence alone - they exist in an external (nonphysical) “substance” just as the human being is external to the computer algorithm being studied in the analogy. The preferences of the agent are analogous to the preferences of a human being who dresses up a virtual avatar, you can still make pretty good predictions based on past behavior but there is not necessarily a direct causal chain. And so libertarian free will is an emergent phenomenon between the physical and nonphysical substances.
It’s also based on a falsifiable premise - that the physical world is indeterministic.
~Max
P.S. This post should answer @begbert2, too