I have always thought that this was best illustrated by this analogy... It is said, "You can lead a horse to water, but you can't make him drink". But, you can lead that horse in the wilderness until it is thirsty enough to drink! But, is it really completely irrestible? I mean if for some reason the water has a smell, and that horse is convinced that it is poisoned, will he not continue to refuse to drink until he dies of thirst? Consider: Heb 12:25 See that ye refuse not him that speaketh. For if they escaped not who refused him that spake on earth, much more shall not we escape, if we turn away from him that speaketh from heaven: It would seem that being able to refuse HIM, or to Turn Away, presumably by free-will and self choice is a possibility? So, how is God's Grace irresistable?