For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. (John 3:16 KJV)
Sacrifice…substitution…surrender…
This seemed to be the theme of this past episode ” 316″ .
Locke : Surrendered himself to the Island’s “expectations”
Substituted 
Christian Shephard with himself
Sacrificed his life as a means of doing that
Jack : Surrendered his need for “proof”
Substituted the “ridiculous” with ” will it work”
Sacrificed his pride , changed the shoes and read the letter
Other “surrenders” …
Sayid : Surrendered to the Marshall (which got him on the plane)
Kate: Surrendered Aaron to something/someone unknown
Sun: Surrendered her thirst for revenge
Hurley: Surrendered to the idea of having Ben around
Ben: Surrendering to the fact that he can legitimately get beat at his own game ( as well as just beat 
)
Frank : Surrendering to the knowledge that ” We aren’t going to Guam, are we?” 
And there were substitutions galore in the flight 815 reenactment:
Jack for Locke in his “faith journey”
Kate for Jack in the “skeptic” role
Hurley carrying a guitar case like 
Charlie
Kate with the Marshall is now Sayid with the Marshall
Kate may possibly be “The pregnant girl” like 
Claire ( and in turn, may prove perilous)
Ben was late like Hurley
Jack with letter/ 
Sawyer with letter
Frank for Seth , as the pilot
Man in line at airport lending sympathy to Jack for his loss… standing in for Ana Lucia
Sun with ring, hopeful about husband, 
Jin, being alive … Rose/Bernard
Jack and Claire half/brother & sister, 
Boone and 
Shannon step brother and sister
Kate with issue with not being with her “son” Aaron / Michael
and 
Walt
Jack with substance abuse problem/ Charlie with substance abuse problem
Jack’s letter “reappearing”/ Sayid’s picture of Nadia “reappearing”
Ben and Walt possibly having the same “specialness” , discovered in childhood (?)
Jack and Kate in estranged relationship/Jin and Sun
(IMO) Awkward “moment” between Jack and Kate, prior to flight, reminiscent of Boone/Shannon (different context, though)
Jack saving others through burning wreckage… now jumping off of waterfall to rescue ( Fire + Water {?} )
And in the end, they all sacrificed what they thought they wanted, finally being “home”, to what was “supposed” to happen, being on the Island.
But 
Desmond… he’s through with the Island, brotha! At least, for now anyways. 
