Let Nature Take Its Course Meaning

Example : 1916, Peter B. Kyne, Cappy Ricks, ch. 27:  "Do you mean to put a secret-service operative aboard disguised as a deckhand?"  "Huh! Skinner, you distress me. I'm going to put Matt Peasley aboard the Quickstep as second mate, and let Nature take its course."1917, Ring Lardner, Sr., "The Water Cure" in Gullible's Travels:  A boat trip to St. Joe! I and the Missus and the two love birds. And I'd see to it that the chaperons kept their distance and let Nature take its course.1984, Piers Anthony, On A Pale Horse, ISBN 9780345338587, p. 145:  I have slashed veins in my ankles and am pleasantly bleeding to death in this hot water. There is no greater kindness you can do me than to let nature take its course.2005, Cardinal Cormac Murphy-O'Connor, "If God died for all of us, it is not ours to decide who is fit to live," telegraph.co.uk, 27 March (retrieved 2 Sept. 2010):  Her life is not worth living, people say; see, she is dependent on others even for food and water; let nature take its course.