Free will

About
Free will (FW) is a phrase often used in philosophical discussions, but also often without clear definition. This often results in strong disagreements over its implications arising from the fact that the disputants are talking about different concepts.

Working Definition
Free will can be defined as
 * that attribute which exists when your decisions
 * cannot be predicted or controlled by others
 * are based on accurate perceptions of reality
 * the ability to rationally disagree with others
 * the ability to make independent decisions based on data of a non-predetermined nature
 * Example: a thermostat might be able to make a decision about whether to trip, but it must be fed temperature data in a particular format. It can't make use of other information to make that decision, in the event that its thermocouple becomes unreliable.

These definitions seem to be in line with the lay understanding of the phrase "free will".

Other Definitions
When discussion of "free will" gets more intensely ideological, the implication seems to be that in order for "free will" to exist, it must be one or more of the following:
 * non-deterministic ("hard determinism" states that free will cannot exist)
 * non-algorithmic
 * not within the physical body
 * outside the realm of science and rational analysis

This definition seems to be more the definition of the term when it is being discussed by skeptics such as PZ Myers, who rightly deny the likelihood of any such thing (given the lack of evidence) -- or that it is even meaningful to attempt rational discussion of something that is outside the realm of science.

...with Determinism
As an example of how determinism is compatible with the working definition of free will, consider the following:

A Mandelbrot set is deterministic — but can you tell what color any given point is going to be before you actually do the calculations? The equation is essentially displaying "free will" within the limited universe of inputs it is given; we can't predict what it is going to do without actually going through the exact same process.

Similarly, if I display free will in making a decision, I can't know what answer I'll come up with until I actually do the thinking, and you can't predict what answer I’ll come up with unless you have all the same information I’m working with (including internal states).

...with Algorithmic Processing
Algorithms are a superset of deterministic processing, in that random elements may be among the inputs. If you can have free will without random elements, you can certainly have free will if they are included.

Related

 * Free Will, a short e-book by Sam Harris arguing against the idea
 * critiques: Woozle

Reference

 * , as expected, takes the view that FW is "impossible in a solely naturalistic system in which biochemical processes obey natural laws, not will."
 * takes a more balanced approach, including some analysis of Christian "free will".
 * takes a more balanced approach, including some analysis of Christian "free will".