[Note: I wrote this as a draft months ago intending to do some heavy revision on it before posting it. I never got around to that. Jeremy has hinted that I should just go ahead and post it, but I was reluctant because I felt like it needed more work. But I'm busy, so I'm never really going to put more work into it. And now, in light of the SCOTUS ruling yesterday (day before?), this is suddenly relevant again. So, hey--these may be only half-formed thoughts, but they are relevant half-formed thoughts, and if ever there was a place for half-formed thoughts, it's the internet, right? So here goes...]
John 10:17-18 reads: "For this reason the Father loves Me, because I lay down My life so that I may take it again. No one has taken it away from Me, but I lay it down on My own initiative. I have authority to lay it down, and I have authority to take it up again. This commandment I received from My Father." (NAU).
This raises the odd question--when Jesus was crucified, did the cricifixion kill Him or not? Or, more to the point, was Jesus killed, or did He commit suicide?
By the way, "Both" does not seem to be an appropriate answer here.
Historically, on the face of it, it seems that Jesus was killed. But digging deeper raises questions. John notes that "So the soldiers came, and broke the legs of the first man and of the other who was crucified with Him; but coming to Jesus, when they saw that He was already dead, they did not break His legs." (John 19:32-33) This indicates that the soldiers expected Him to still be alive, just like the ones he was crucified alongside. Crucifixion should have taken longer to kill Him. (And as the people in pretty much every bible study I've been in like to point out, John 19:34 indicates that Jesus died of a "broken heart".)
Theologically, there is reason to doubt that Jesus was killed as well. First of all, there is the John 10:17-18 quote which indicates that no one takes Jesus' life away, but that He lays it down of His own accord. This corraborates nicely with John 19:30 where Jesus gives up His spirit. Furthermore, Jesus is the Life; is there any force in the universe that could take His life away from the very incarnation of Life?
This indicates that Jesus committed suicide in some sense. He lay down His life--it wasn't taken from Him. While Jesus didn't actively cause physical damage to Himself, the physical damage that was done to Him doesn't seem to be what caused the end of His life. Jesus died because He lay down His life/gave up His spirit. That would have caused His death even if He had been in perfect physical condition. Conversely, His wounds wouldn't have killed Him had he chosen not to lay down His life.
Resistance to the idea that Jesus committed suicide comes maily from two ideas: First, the idea that suicide is always a moral wrong. If suicide is always a sin, and Jesus was sinless, then Jesus must not have committed suicide. However, it is not at all clear that suicide is always a sin. The act itself is not clearly prohibited. And while almost all suicides are done from wrong motives, and thus are sinful, it is certainly possible that one could do so with entirely noble intentions. If one were to sacrifice oneself to save others, that seems to me to be moral, not sinful. And, of course, this is precicely what Jesus did in His death.
The second idea that causes resistance is the idea that Jesus must have suffered the greatest possible physical suffering in His Passion. Frequently I've been told that crucifixion is the most painful suffering possible. I'm not sure how that is possible since technology now exists to make much more painful deaths possible, but even if it were true, Jesus died too early to experience all of that pain. There seems to be some (in my opinion entirely unbiblical) theological notion that Jesus' physical suffering is the payment for our sins. And thus, for Him to pay for our sins, He must suffer more physically than anyone else ever. I don't know where this idea comes from, but it seems to be there nevertheless. At any rate, people who hold this idea resist the idea that Jesus committed suicide because they feel that this somehow decreases the amount of suffering that Jesus endured (even though these two ideas in no way conflict).