Freewill... is an illusion. However, because human beings experience gratitude and resentment, the argument comes to a definite albeit tricky close. Aside head injuries and certain afflictions, human beings are married to gratitude and resentment. And yet, in the face of the phantom, gratitude and resentment presuppose the literal existence of freewill. Within this goofy tracery, I find the very fact that we have ability to examine our circumstances from a high enough orbit to make these sorts of examinations is a testament to the possibilities of human understanding. Here is the IEP summary of Peter Strawson's contribution to the question.
Strawson’s Reactive Attitudes
The IEP page: http://www.iep.utm.edu/freewill/#SH5c
Chrysalis, a growing collection of very short fiction.
Unless noted, all pics credited to Skitz O'Fuel.