He gave you an adequate explanation as to why he believes we have free will. What is your reasoning for believing we have no free will and it is therefore an illusion?
This is part of the problem here.
People are assuming that if freewill is illusory then it doesn't exist.
But if it is illusory it still continues to operate in the the same manner as it does for everyone who thinks it genuine.
It is not a case of saying "there is no freewill".
It is merely understanding what that freewill is.
As another has given as an example, a mirage still exists the same as it always does whether we consider it an illusion or not.
What is illusory is what it is depicting.
Our perception.
It sounds to me that in the case of moving his arms, when, where, and how he feels (within the limitation of his body), he himself is the cause of the said effect. I suppose if he should ever have a stroke, or become paralyzed, not being able to move his arm according to his instruction, then his will to move them on a whim would be lost, hence he cannot freely, will his arms the way he once could. There's a example of free will right there.
There's an example of the appearance of freewill.
We are judging our notion of "freewill" in that example by how it appears to ourself.
Okay, it's become obvious to me that for you, there is no question as to whether or not free will is an illusion. Why is it an illusion?
Sorry if you have covered this already. If that is the case then please point me to the post.
For me it is because the requirement for a genuine freewill is for the self to be the absolute instigator of an action.
If we start with the premise that actions are all caused by other actions, and the outputs of those actions are governed by the laws of the universe, whether deterministically or in deterministically, then for our freewill to be genuine we would require something that does not adhere to the premise.
That we perceive this to be the case leads to the conclusion that it is just a perception.
That we perceive ourself to be the instigator whereas we are actually just the end result of a vastly complex set of interactions.
Determinism or indeterminism does not matter.
What matters is that we can not alter the laws of the universe, and that the result of an interaction - at the micro level - is in accordance with those laws.
Others have said "indeterminism... therefore freewill"
But that don't explain how one leads to the other, only that one is a prerequisite for the other.
And everything most people (I.e. the advocates of a genuine freewill) say starts with one's conscious perception being the arbiter of what freewill is or isn't.
And by doing so they have zero means of establishing whether freewill is illusory or not.
Their definitions of freewill start with the implied notion that it is a perception.