Aquinas' Cosmological Argument

 

Simply stated:

 

Of the things we observe, all things have been placed in motion. No thing has placed itself in motion.

 

Working from the assumption that if a thing is in motion then it has been caused to be in motion by another thing, Aquinas also notes that an infinite chain of things-in-motion and things-causing-things-to-be-in-motion can not be correct. If an infinite chain or regression existed among things-in-motion and things-causing-things-to-be-in-motion then we could not account for the motion we observe. If we move backwards from the things we observe in motion to their cause, and then to that cause of motion within those things that caused motion, and so on, then we could continuing moving backwards ad infinitum. It would be like trying to count all of the points in a line segment, moving from point B to point A. We would never get to point A. Yet point A must exist as we know there is a line segment. Similiarly, if the cause-and-effect chain did not have a starting point then we could not account for the motion we observe around us. Since there is motion, the cause and effect chain (accounting for motion) must have had a starting point. We now have a second point:

 

The cause and effect relationship among things-being-moved and things-moving must have a starting point. At one point in time, the relationship was set in motion. Thus, there must be a First Cause which set all other things in motion.

 

What else can we know about the First Cause? The first cause must have been uncaused. If it were caused by another thing, then we have not resolved the problem of the infinite regression. So, in order to account for the motion that we observe, it is necessary to posit a beginning to the cause and effect relationship underlying the observed motion. It is also necessary to claim that the First Cause has not been caused by some other thing. It is not set in motion by another entity.

The First Cause is also the Unmoved Mover. The Unmoved Mover is that being whom set all other entities in motion and is the cause of all other beings.

 

For Aquinas, the First Cause, Unmoved Mover is God.  In contemporary language, we could ask the question "What started the universe?".  Many are quick to say "The Big Bang" but that doesn't answer the Basic question when we note that something had to "wind up" the Universe.  The Second Law of thermodynamics  states that all matter is going to a lower form of energy, to a more random state.   The energies observable, and potential energy locked up in matter needed to get that way somehow.  Ergo, A First Cause.