Modal Versions of the First Way

I'm actually finding more time to post entries on this blog than I initially expected, which is nice, because I truly enjoy the diverse interactions.  Here's how one might formulate a modal version of the argument from motion, with the use of a weakened Principle of Sufficient Reason (W-PSR)

1. Possibly, everything that exists has an explanation of its existence, either in the necessity of its own nature or in an external cause. (Premise)

2. Possibly, everything that changes has an external and sustaining cause of its change. (Premise)

3. Necessarily, the regress of external and sustaining causes of change is either finite or infinite. (Premise)

4. Possibly, the regress of external and sustaining causes of change is finite. (Premise)

5. Necessarily, if there is a first cause in the order of sustaining causes of change, that cause is immutable, e.g. an Unmoved Mover. (Premise)

6. Hence, an Unmoved Mover possibly exists. (From 2, 4, and 5)

7. Necessarily, an Unmoved Mover cannot be externally caused. (Premise)

8. Hence, an Unmoved Mover exists by a necessity of its own nature. (From 1, 6 and 7)

9. Therefore, an Unmoved Mover exists. (Implied by 8)

Another modal version might look like this:

1. Possibly, everything that exists has an explanation of its existence, either in the necessity of its own nature or in an external cause. (Premise)

2. Possibly, everything that changes has an external and sustaining cause. (Premise)

3. The universe as a whole is constantly changing. (Premise)

4. Hence, the universe's change possibly has an explanation.

5. Possibly, the universe does not have to change. (Premise)

6. Possibly, the change of the universe is explained by an external cause, e.g. an Unmoved Mover. (From 1, 3, and 5)

7. Hence, an Unmoved Mover possibly exists. (Implied by 6)

8. Necessarily, an Unmoved Mover cannot be externally caused. (Premise)

9. Hence, an Unmoved Mover exists by a necessity of its own nature. (From 1, 7, and 8)

10. Therefore, an Unmoved Mover exists. (Implied by 10)

To reiterate, we may infer some modest divine attributes.  Given that the external cause of the universe's change must transcend the universe (the sum total of all physical, space, time, matter and energy), the Unmoved Mover must be timeless, changeless, immaterial, and very powerful.  A good case can be made for additional attributes, but I'll leave that issue aside for now.