How was Sauron destroyed?

[Arnizipal]

When the One Ring was destroyed, why did Saron "die" along with it? It is said in the novel that he could take physical form, so why would he lose this ability just because he permanently lost his Ring? Sauron seemed to do just fine even without it....

[Iracundus]

Sauron had invested the majority of his original innate power into the Ring. While the Ring existed, Sauron was not diminished in his might. The sum total of his being was still intact. If he wore the Ring, his powers would even be enhanced. When the Ring was destroyed, the majority of Sauron's native power dissipated and he was thus reduced to an impotent formless spirit, as what he had leftover in himself was only a small fraction of what he was in the beginning.

It is all part of Tolkien's theme (as he wrote in his Letters) of the dichotomy of power: that is in order for power to be wielded to achieve great results it also must be put forth and put at risk.

[canucklhead]

All of what Iracundus said, + this.

maiar were bound to Arda, and when they were defeated in battle or otherwise destroyed, they became formless echos, spirits that hovered in the veil between Arda and the void, waiting for the end of time.

This would have applied to Sauron. The idea was that evil as an actual being was gone from middle earth. Now man would build the world, with evil being only a shadow, a thing that lived in the heart, more in line how we perceive it.

[Whitwort Stormbringer]

When the One Ring was destroyed, why did Saron "die" along with it? It is said in the novel that he could take physical form, so why would he lose this ability just because he permanently lost his Ring? Sauron seemed to do just fine even without it....

Another way to look at it is that the only reason Sauron could take or maintain physical form (after the forging of the ring) is that he had invested so much power into it that it was his anchor to the physical world. Remember that once defeated and with the ring gone, it took Sauron a loooooooooong time to regain any sort of physical form, and even at that he was severely weakened without the ring actually in his possession. With the ring destroyed, he loses his tenuous grasp on the physical realm and winds up joining Morgoth in the Void.

[DeadInTheHead]

Another way to look at it is that the only reason Sauron could take or maintain physical form (after the forging of the ring) is that he had invested so much power into it that it was his anchor to the physical world. Remember that once defeated and with the ring gone, it took Sauron a loooooooooong time to regain any sort of physical form, and even at that he was severely weakened without the ring actually in his possession.

Yes, he invested a great deal of his power in the Ring, so that he could control the other Great Rings; a side-effect of this "power transfer" seems to be that whilst the Ring existed he could not be "destroyed". Not possessing the Ring mainly meant that he operated with greatly reduced power compared to how he would be with the ring.

With the ring destroyed, he loses his tenuous grasp on the physical realm and winds up joining Morgoth in the Void.

I don't think he ends up in the Void: the Valar forcibly (physically ?) put Morgoth into the void at the end of the first age, but what happened to Sauron was a bit different. I'd say that he wasn't fully destroyed, but what was left with the destruction of the ring was so weakened that it amounted to much the same thing - a spirit of spite and malice, with no more power than a ghost.