u/Careful_Thanks_5500

Either time belongs to the world or it does not.

If it does not, this is impossible, since the world is defined as the sum of all that exists.

Hence, time belongs to the world.

If time belongs to the world, then time is either eternal or began to exist.

But if time began to exist, this appears incoherent, because time itself constitutes succession and temporal priority; nothing can exist temporally prior to time in order to bring it into being. That would amount to explaining time through time itself.

Therefore, time is eternal.

And if time is eternal and is included within the world, then the world itself is eternal.