My friend and I had this debate about a battle between Lavos and Magus; who would win? I mentioned that if Magus could beat Lavos, the Apocalypse in 1999 wouldn't happen, because Magus would have summoned Lavos in 600 AD, and defeated him right there and then, thus, the Apocalypse wouldn't have happened. However, since the Apocalypse in 1999 did happen, Magus obviously failed at killing Lavos, thus dieing (Or losing to Lavos).
My buddy countered that Magus didn't fight Lavos, that Crono and his crew interrupted Magus summoning Lavos, thus we can't accurately say whether or not Magus could have defeated Lavos on his own. I then reminded him that if he could have defeated Lavos on his own, the Apocalypse in 1999 wouldn't have happened, and thus the Crono crew would have no reason to try to change the past (which would have led them to the year 600 AD).
My buddy then pointed out that if Magus was supposed to lose if the Crono crew didn't show up to screw up the summoning, why didn't the world become destroyed in 600 AD. I mentioned that just because Magus woke up Lavos doesn't mean the world will be entirely destroyed; for example, in 12,000 BC, only the floating islands were destroyed.
He then mentioned that if Crono didn't go back in time, then Zeal would have gone on to absorb Lavos indefinitely, thus the Zeal Kingdom would still be in power in the present time. I commented that even without Crono's interference, the fall of Zeal was invertible, because if it didn't happen, Janus (AKA Magus) wouldn't have been sent to 600 AD, which leads him to summon Lavos to fight (Which he would lose the fight against, as proven in the 1999 Apocalypse). He asked me how the events would have unfolded without the Crono Crews interference, and I replied I dunno.
He exclaimed that was his point. Since the subject of time-traveling is so innately complicated, discussing what-ifs are pointless; that you can not make educated guesses on how the time-line would have been without the Crono Crews interference, and he added that, Crono was destined to time-travel. I pointed out that one of the many themes in Chrono Trigger and Cross was that man, not Gods, were responsible for their own destiny, that they and they alone have the ability to change their path in life; that time is not set in stone. He countered with that since Crono Trigger is a video game, that Crono will always time-travel, and thus, it is indeed predetermined. I honestly had no counter against that, 'cept, "Gah, I hate the 'it's just a video-game' argument...".
In short, the two disagreements I have with him is:
1. He believes you cannot make educated guesses on how the original time-line would have went without the Crono Crews interference.
2. And he believes Crono's destiny was in fact, predetermined.
So, experts of the Chrono series, what's your say in all this?
PS, I posted this at gamefaqs, and one of the posters mentioned the Masamune. To quote him:
"Interesting theory, but how would you explain the already existing Masamune loop? The sword with Melchior's name engraved would never have ended up in the past if it weren't for Crono. Therefore Cyrus would not have been able to fight Masa and Mune for the sword before Crono and team got to it because there'd be no sword."
Unfortunately, it's been years since I last played the game, and I can't think of a way to counter that statement.