Is volition a reality or an illusion? Keeping religious sentiments aside, here is a question raised on the Buddhism SE that attempts to answer a similar question from the Buddhist point of view.

You see, Buddhism has a concept of anatman or no-self that attempts to explain the conditioned-self as a cause-and-effect phenomena arising through the interaction of the five aggregates (sensations, mental-formations, thoughts, feelings, etc.) and doesn't have a permanent or essential existence of its own. However, I would like to know what does the science or psychology has to say about this?

Does something called I exists as a soul/essence separate from the physical body? More importantly, does volition, or more commonly called will-power exists or it is just an illusion?

A practical Experiment:

Suppose I (as soul/mind/any-other-hypothetical) decide to lift my arm right now, and the very next instant my arm lifted in the air. I would like to know what exactly triggered the decision to lift? If it were I (soul/mind/etc..) that made the decision, then why would  electrodes attached to my brain show that the impulse to move the hand came before I was aware of it? The electrodes reading seem to imply that:


Either the arm has a mind of its own apart from the primary mind (sort of a separate CPU core in a multi-core processor) that took the decision (seems less likely to me). OR
Some external force (in nature) triggered the decision (seems more likely to me).


I would like to know what is Psychology's take on this?

EDIT: The conventional explanation to this in terms of the subconscious being the causal factor seems incomplete at best. As mentioned in a comment on @ArnonWeinberg's answer, all it means is that we don't know. Subconscious seems like a hypothetical chaos that we ascribe all phenomena that we are unable to explain scientifically. In the above experiment for instance, what caused the subconscious mind to make that decision at that exact moment?
This question is very similar to others on this forum, and I think almost everything in the question is answered there.

Does something exist separate from the physical body?

I don't think you will find the answer to that question in cognitive science, but rather in philosophy.  Taken from one of the answers:


  Your thought experiment hinges on the debate of materialism (the mind
  is a physical thing) versus dualism (the mind is a different kind of
  thing than other physical things). Most cognitive scientists believe
  that materialism is the correct view.


It is unclear whether or not science will ever definitively settle this question, but it may place some constraints on the role (if any) of non-physical entities.  As I mentioned in my reply:


  The large body of research that was spurred on by Libet's experiment
  has significantly changed our understanding of the role of "thought"
  or "will" or "volition" in the causal chain, such that they now appear
  to be a side-effect rather than cause of physical action.


Why would electrodes show that the impulse to move the hand came earlier than I was aware of it?

I think you are missing a 3rd option: Much of what happens in the brain is outside of our awareness.  This is called the unconscious mind.  The brain is a very complicated system, so exact causes for behaviours are still elusive, but the implication behind the Libet experiment is that the decision to move is made unconsciously - still inside the brain, but outside awareness.

EDIT (re updated question):

I'm not sure what you mean by "Subconscious seems like a hypothetical chaos that we ascribe all phenomena that we are unable to explain scientifically"...  Non-scientific terms such as "soul" or "mind" or "will" certainly fall under that category, as they don't add any information, and there are no tools available to study them, thus we know nothing about them.  The "unconscious mind" on the other hand, refers to physical, measurable processes in the brain, just ones outside our conscious awareness.  Cognitive scientists learn about unconscious processes through cognitive research, fMRI scans, and other tools of neuroscience for example.  Thus we have a great deal of knowledge about how the unconscious mind works.

What causes the unconscious mind to make decisions?

Again, this question comes down to the choice between materialism and dualism - the choice is yours to make.

Consider a simpler question: Say a computer makes a beeping sound a few seconds after someone presses a key - what caused it to do that?  (1) The computer needs a speaker with which to make the sound (hardware); (2) the computer needs a program that uses the speaker (software); and (3) it needs a user to press a key to run the program (input).

Now consider a much more complex machine: Say a human lifts their arm a few seconds after someone says "atten-hut!" - what caused them to do that?  (1) The human needs an arm to lift (biology); (2) the human needs to know when to salute (learning); and (3) they need someone to call them to attention (stimulus).  Like any machine, all actions are a result of its internal mechanisms, current state, and external environment.

But what if the computer makes a beeping sound with no one around to press a key?  Maybe at some point in the past someone ran a program that makes beeping sounds randomly every once in a while.  Or maybe it did it of its own "free will"?  What do you think?

And what if a human lifts their arm with no one around to salute?  Maybe at some point in their past, the person learned to salute for fun when they are bored and alone.  Or maybe it was their "free will"?  What do you think?