Recently I read a newly published very short book criticisng the concept of Free Will. I thought the book made some good points and some not-so- good points, but what really disturbed me is that the author didn't ever carefully define what he meant by Free Will. Is the definition of Free Will so obvious and clear that there is no need to define it in a book intended for lay readers?

You're right to be disturbed if the author never defines 'free will' in a book criticizing the concept of free will! One frequent obstacle to progress in discussing free will is that different parties to the discussion rely on different (and often unstated) conceptions of free will. Some think of free will as whatever is necessary and sufficient on the part of an agent to make the agent morally responsible for his/her action. Some think of it as requiring the ability to have acted otherwise than one in fact acted. Some think of it as requiring the ability to have acted otherwise than one in fact acted even under the same circumstances that preceded one's action. Those conceptions of free will aren't the same -- or aren't obviously the same. It's a good question which of those conceptions, or which other conception, best fits the way we use the concept of free will (assuming we use the concept in a stable way). It's another good question how well those conceptions stand up to scrutiny. In answering those questions it's crucial not to confuse the different conceptions, and failing to define what one means by 'free will' only invites such confusion.

It sounds like you might be talking about Sam Harris' new book, Free Will. If so, you might be interested in my review of it at The Philosopher's Magazine here: http://www.thephilosophersmagazine.com/TPM/article/view/15359/12081

Much of my response focuses on Harris' confused definitions of free will. The answer to your question is a definitive NO: free will does not have a single or obvious definition such that it need not be defined when discussed, especially in a book that claims we lack free will (what exactly do we lack? and do we care about the thing we are being told we lack?)

Eddy: Nice article! I'm glad they tapped you to review Harris's book. (I too suspect that it's the book the questioner is referring to.) --Steve

Read another response by Stephen Maitzen, Eddy Nahmias
Read another response about Freedom