We left Aristotle talking about causes. Insofar as he believed that the universe was one complex machine and that everything in existence was there for a purpose, sooner or later he had to face the problem of what is the ultimate cause of everything?
Aristotle’s answer was that there was a Prime Mover
Aristotle
The Prime Mover is the originating cause of everything, all events and all motion. It follows then that the Prime Mover must exist necessarily and cannot itself be caused.
It is the source of movement, goodness and all change, but itself is not affected by any of them. The Prime Mover is unchanging, can’t improve itself and lacks nothing. As such it may be wondered at, admired or even loved, but it does not respond and is not affected by man’s opinion. It is pure actuality with no potential.
Sadly in his book Metaphysics, Aristotle linked the idea of the Prime Mover with God. This causes quite a number of problems for students, because they all come with preconceived ideas about what God is like, but when these are compared with the Prime Mover they cause confusion.
It is easy to see why Aristotle did so. He wanted to say that thePrime Mover is "a living being, eternal, most good, so that life and continuing existence and eternity belong to God". But he also draws attention to the fact that the Prime Mover is not concerned with the day to day running of the world. It does not feel sympathy answer prayer or alter the course of history. It is not concerned with angels, not affected by evil or problems about its origins, has no son or other offspring and does not make attempts to "save" the world in any respect.
Once one grabs the basic idea, it becomes easier to understand where Aquinas in coming from in his Cosmological argument. The unmoved mover is just a reusing of Aristotle’s concept.
