What is "God"?

I wish to begin with a quote from Albert Einstein . When asked  if he believed in God by Rabbi Herbert Goldstein; Einstein responded, "
"I believe in Spinoza's God who reveals himself in the orderly harmony of what exists," not in a God who concerns himself with fates and actions of human beings."
Albert Einstein: Philosopher-Scientist edited by Paul Arthur Schilpp (The Open Court Publishing Co., La Salle, Illinois, Third Edition, 1970) pp. 659 - 660
So today we look at Spinoza`s answer to the question: What is God? Baruch Spinoza (1632-1677) was a Dutch philosopher with Jewish parents. He was brilliant as a youth; and his brilliance promised him a bright rabbinical career. However his ideas proved to be too controversial for the time, and he was eventually excommunicated from the Jewish circles. His greatest work "Ethics" was only published after his death; we must remember that at the time, to oppose the established religions in anyway was asking for trouble to say the least. I urge anyone who is interested to find out more about this very influential philosopher to read Ethics and  Theological Political Treatise. There are also some great modern works on Spinoza by Prof. Steven Nadler  on Amazon.
We first begin with what God is not.Spinoza believed that God is not anthropomorphic. In other words God does not portray human characteristics. In the Bible we read that at various times that God is angry or wrathful, repentant etc. Understanding history is very important here also; in the times the Bible and other ancient religious text were written, the main style of government was the Monarchy. So we can see that the "God" of the religious texts reflects this. God has a "throne" and "servants" or attendants. According to Spinoza; God has none of these attributes; God is not concerned or involved with human affairs or providing divine assistance in any way.
Spinoza`s God is identical with nature; however a common misconception made by many is to label Spinoza a Pantheist. This is an error because according to Spinoza, God is not "in" all; but God "is" all. Now people may say "Does that mean God is a Rock or Tree? No; this would be a gross misunderstanding. I like to explain it this way. If we take any object in the universe and break it all the way down to its smallest particles; you will see that everything in the universe is made of the same substances. Let us take a look at the periodic table of elements. The only differnce between the elements lies in the amount of protons,neutrons and electrons. So Hydrogen for instance; has one proton and Hydrogen has two. However they have different attributes. Let us take our breathable Oxygen; O2. In nature Oxygen occurs as a "diatonic gas," thus O2(molecule) and not just a single Oxygen atom. The difference between Oxygen (O2) and Ozone(O3); you guessed it! is an extra oxygen atom. This is what we mean when we talk about the "oneness" or "sameness" of all things. Although we see things in nature possessing different attributes; they are all the same in their "core" nature. If we were to continue to break the elements down; we will find that  all of the same particles exist in all elements.
According to Spinoza God is that; which is by nature is self-existant,  eternal, and infinite. This is why there can only be one God; because God is the source of all things in the universe. You can name it what you please; but the attributes must be present for it to be "God." In other words God can`t have a cause; because then that which caused God to exist would then be "God."  The same applies to the "eternalness" of God; by nature God must always have existed. I always am reminded of the First law of thermodynamics "Energy can neither be created or destroyed." God is simply the beginning and end of all things, or  Alpha and Omega; everthing in the universe is just a nother possibility of God manifested.  This led Spinoza to say; "There is one substance in the universe; it is God; and everything else is in God." We are all connected in this way; humans, animals, stars etc. This is why Spinoza used the term "nature" to describe the phenomena; everywhere you look and turn, is just another manifestation or form of "God."We are just different combinations of One substance. Here is a simple way of looking at it: Think of all of the products that are made of crude oil. We have plastic bottles,bags,rubber tires,artificial hearts,band-aids and almost anything else you can think of. Note all of these different things evolve from one substance. This is the same idea of Spinoza; Everything in the universe, Stars, humans,rocks,dogs,guitar stings and whatever you can fathom; all come from the same substance ultimately.As a matter of fact; Try to think of anything in the entire universe that does not consist of the same atomic and sub-atomic particles.Imagine if you could "zoom" in even further; eventually we must reach a place where there is no more breakdown, nothing smaller, and without cause and at the same time has always been (deep!!). It is this eternal,self-generating,infinite force that we call God.
Sources and "Suggested" reading:

Baruch Spinoza: Ethics ;Political Theological Treatise  (these books are so old that you can read them for free online at http://www.gutenberg.org/browse/authors/s#a473   or Purchase them super cheap somewhere.

Steven Nadler Prof. @Univ. of Wisconsin (Chair of philosophy)

Spinoza: A life   (A nice read) http://www.amazon.com/Spinoza-Life-Steven-Nadler/dp/0521552109
In this lecture he gives a nice basic/light intro to Spinoza: http://www.youtube.com/watch?v=mIYOC6RQ_LY

Laws of thermodynamics: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEner1.html

Related is Leibniz idea of Monads : http://www.amazon.com/Monadology-Forgotten-Gottfried-Wilhelm-Leibniz/dp/1605069892/ref=sr_1_3?s=books&ie=UTF8&qid=1287364581&sr=1-3