deadish said:
I would not use the words "against any biological drive". Those don't change baring physical change in your brain structure. We definitely do not have the technology to change it "at will".
Beliefs can most of the time be changed by rational argument - refuting the belief. Of course, this isn't fool-proof as humans aren't completely rational beings.
I have yet to be presented a convincing argument that would sway my opinion and how I feel about this touchy subject - rational or otherwise.
Not necessarily at will, but the saying "fake it till you make it" is certainly accurate to some degree in human behaviour, a conscious choice that you actively enforce to change how you think about something, will eventually change how you think about it. Just like experience will change your subconscious outlook on the world or parts of it, enforcing a decision and going to the effort of changing your own thoughts on something work. Actual and perceived experience are interestingly close in how they affect you.
Define "intelligence".
There are a few definitions, but by true intelligence I mean sapience, hell, there is a thread about it on the Escapist

http://www.escapistmagazine.com/forums/read/18.157686-Sentient-vs-Sapient
I disagree. At the lowest level we are exactly the same. It's just that with our "better" brains, we are more sophisticated at how we go about fulfilling these "drives".
Most of the things you do can be traced to fulfilling one of these :
http://en.wikipedia.org/wiki/Maslow's_hierarchy_of_needs - a list of drives common to a lot of humans.
My point is "free will" is an illusion. We are made up atoms (and nothing more), we are technically just carbon-based, self-replicating, deterministic machines. Cause and effect.
At how we go about fulfilling SOME of them, but people still make choices that they know satisfy no (or at the very least few or less important ones than if another choice was taken) needs.
And most is not all, most of what we do will invariably come from what we need and our basic wants, because we are far from being low-maintenance beings, it is the ones that don't that make a difference that I am pointing out.
It is only at the most basic molecular level pre-determined, from anywhere larger than there the "illusion" of free will is so flexible, so easily altered and unpredictable that in the psychological sense of the word free will, the most basic level is entirely useless to look at. To say whether or not we have free will based on the fact that the universe is at the simplest level perfectly mathematical has no bearing on history, psychology or anything outside of a theoretical discussion such as this one. Machines we may be, but we are machines so unfathomably complex and flawed that our actions are still impossible to predict or determine using the molecular level.
Also, try to make a fair justice system that incorporates that idea, it is simply not practical.