"Never say you know the last word about any human heart." - Henry James Logan Mountstuart, the central character of Any Human Heart , which begins this Sunday on PBS' Masterpiece Classic , has experienced the sort of life that is overflowing with love and loss. It's a portrait of not just a life lived, but also of England in the 20th century. The three-part drama (which aired last year in the UK on Channel 4) is adapted from William Boyd's 2002 novel, "Any Human Heart: The Intimate Journals of Logan Mountstuart," and recounts the extraordinary life of the central character, played throughout his life by Sam Claflin, Matthew Macfadyen, and Jim Broadbent. Told in a non-linear fashion, we witness key moments in Logan's life: his Oxford collegiate days, the blush of first love and fatherhood, wartime encounters, romance and death, success and failure. It's the elderly Logan (Broadbent) who is sorting through the detritus of his life and, it seems, hi