True and saving faith in Christ is not a thing out of the power of man, but infinitely easy. 'Tis entirely in a man's power to submit to Jesus Christ as a Savior, if he will; but the thing is, it never will be that he should will it, except God works it in him.
—Jonathan Edwards, from Miscellanies #71
Edwards draws a distinction here between two kinds of ability:
- Physical ability - having the external means with which to do something, and
- Moral ability - having the internal will or desire to do it.
For some biblical evidence of this distinction, see Mark 10:17-27 and John 3:19-21.