Excerpt from Chovoth HaLevavoth (Duties of the Heart) by R. Bachya ben Joseph ibn Paquda
(Here is a demonstration of the Existence of the Creator) –
Sha’ar Ha’yichud, Section One: The Gate of the Unity of G-D, (Excerpts from Chapters Five and Six) –
There are three premises which lead to the inference that this world has a Creator who created it from nothing:
1) A thing cannot make itself.
2) Beginnings (causes) are limited in number; therefore, they must have a First Beginning (First cause) which had no beginning (cause) before it.
3) Anything composite must have been brought into existence (cannot be eternal, i.e. without beginning).
When these three premises are established, the inference will be, for one who understands how to apply them and combine them – that the world has a Creator who created it from nothing, as we will demonstrate with G-d’s help.
Since it has been demonstrated that there cannot be an infinite series of causes, it follows that the world must have a beginning before which there is no other beginning, a first cause without a cause before it. It is He Who formed the world, bringing it into existence out of nothing, aided by nothing, and with nothing as a foundation, as it says in scripture: “I am G-D Who made all things; I alone stretched out the heavens, by Myself I spread out the earth” (Yeshayahu 44.24); “He stretches out the north over empty space, suspends the globe over nothing” (Iyov 26.7).
Arguments [for the proposition] that G-D is one:
Since it has been demonstrated by way of logical argument that the world has a Creator, it is now our duty to inquire as to whether He is one or more than one. [….]
The first [argument] is drawn from examining the causes of existing things. For when we consider these causes, we find that they are fewer than their effects. [….] The further back we go in tracing the cause of causes, the fewer causes we find; the higher we ascend [the hierarchy of causes], the lower their number becomes, until finally, when we reach [the top, there is only] one cause, the cause of all causes.
To read more on line, go to Daf Yomi Review, Chovoth HaLevavoth.