Jonathan Edwards 
The Nature of True Virtue [PDF ebook] 

A major work in moral philosophy by the Puritan who was the most modern man of his age.
Edwards at his very greatest . . . he speaks with an insight into science and psychology so much ahead of his time that our own can hardly be said to have caught up with him.
Perry Miller, 'Jonathan Edwards’
Like the great speculators Augustine, Aquinas, and Pascal, Jonathan Edwards treated religious ideas as problems not of dogma, but of life. His exploration of self-love disguised as true virtue is grounded in the hard facts of human behavior.
More than a hellfire preacher, more than a theologian, Edwards was a bold and independent philosopher. Nowhere is his force of mind more evident than in this book. He speaks as powerfully to us today as he did to the keenest minds of the eighteenth century.