During the Rambam's time, there was a proliferation of heretical sects and Jews were often called upon to explain their beliefs in comparison to other faiths. The Rambam, in response, decided to set down 13 Principles of Faith which encompass the crux of Judaism. Let every Jew, and non-Jew, learn and take these Principles to heart for without them, one's spiritual growth will be stillborn. It is taught that one who denies them has no share in the World to Come! The First Principle is especially important as we approach Pesach, when G-d demonstrated to the entire world His power.
"I believe with perfect faith that G-d is the Creator and Ruler of all things. He alone has made, does make, and will make all things."
To believe in the existence of the Creator, and this Creator is perfect in all manner of existence. He is the cause of all existence. He causes them to exist and they exist only because of Him. And if you could contemplate a case, such that He was not to exist…then all things would cease to exist and there would remain nothing. And if you were to contemplate a case, such that all things would cease to exist aside from the Creator, His existence would not cease. And He would lose nothing; and oneness and kingship is His alone. Hashem of strength is His name because He is sufficient with His own existence, and sufficient [is] just Him alone, and needs no other. And the existences of the angels, and the celestial bodies, and all that is in them and that which is below them…all need Him for their existence. And this is the first pillar and is attested to by the verse, “I am Hashem your God.”
G-d's existence is the foundation of life. HaShem created the entire world from absolute nothingness through His speech. Before the world, He reigned alone, and after the world, He will reign forever.
HaShem is an absolute and everything else is dependent on Him. He exists because He exists, and it is inconceivable that He not be. Everything that is in existence only exists by virtue of the fact that He will it to exist. There is no power outside or besides Him. He is the Prime Mover and the First Cause.
Recognizing G-d is the most basic and crucial aspect of life. Once we accept that the Creator is Absolute, we can accept that His law is Absolute. We must come to know that we each play an important role in the vast mechanism of creation. The Almighty is the Mekor Chaim, the Source of Life, and to be able to live a proper, moral and meaningful life, one must recognize the Source. The Torah tells us: "Be careful lest your heart be misled and you turn aside and serve other gods" (Deuteronomy 11:16). "Turning aside" means straying from the Torah; once you stray from the Torah you will cleave to and serve idols (Rashi quoting Sifri on Deuteronomy 11:16). There is but one choice: to serve G-d or to serve idols. Once man strays from G-d's Truth, the Torah, he creates new rules for himself and invents new moral standards. One who does not worship HaShem worships himself, placing his trust in his own frail abilities, in his talents, skills, money, or strength. These things are emptiness and vanity! They have no strength other than what HaShem gives them! If a person does not serve G-d, he serves an illusion, the fancies of his own limited mind.
By accepting G-d's supremacy, man fulfills his purpose in creation. Rashi comments on the first verse of the Torah- Bereishit barah Elokim- for the sake of Reishit, the Beginning, G-d created the world. "The world was created for the sake of the Torah which is called 'The beginning of His way' (Proverbs 8:22), and for the sake of Israel who are called 'The beginning of His grain crop.'(Jeremiah 2:3)". The entire world was created for the sake of the Torah, G-d's Blueprint in creation which He gave to guide people towards Him, and for the sake of Israel, the nation that testifies to His existence. When a Jew declares morning and evening "Sh'mah Yisrael, Hear O Israel, HaShem is our G-d, HaShem is One", and accepts the yoke of heaven upon himself, he brings the world to a higher degree of perfection.
The difference between this world and the World to Come is that in this world, G-d is in hiding. He is not apparent and one must search hard to find Him. In the World to Come, HaShem will be apparent. There will be nothing that separates us from Him.