HaShem Echad! - HaShem is One!

I am certain, with complete certainty, that the Creator, blessed be His Name, is One and there is no unity like His in any way. He alone is our God – He was, He is, and He will be.

From the Siddur.

The Second Foundation [of the Thirteen Foundations] is the unity of HaShem, blessed be His Name. In other words, [the Torah teaches us] to believe that this Being, which is the Cause of all, is one. This does not mean one as in one of a pair nor one like a species [which encompasses many individuals], nor one as in one object that is made up of many elements, nor as a single simple object that is infinitely divisible. Rather, HaShem, blessed be His Name, is a unity unlike any other possible unity.

This second foundation is referred to when [the Torah] says, "Hear Israel! HaShem is our God, HaShem is one". (Devarim [Deuteronomy] 6:4)

From the Thirteen Foundations by Rabbi Moshe ben Maimon.

The belief in the unity of God is one of the most basic elements of Jewish belief. The basic ideas of this belief are very simple. Judaism teaches that the Creator is absolutely unique and indivisible. Belief in another god in addition to HaShem is considered idolatry. Furthermore, HaShem has no parts or sections. He is absolutely One and cannot be divided further. Belief in the unity of HaShem is a mitzvah that can be fulfilled at any time just by thinking.

There are many additional important principles that we derive from this basic statement of Jewish belief that "HaShem Echad" - "HaShem is One." Among these are the following:

• HaShem is unique in His perfection. No other being can compare to His perfect kindness, love, truth, and justice.

• HaShem is the only one who controls the universe. Even the "laws of nature" are only the constant expression of His direct Will. All that occurs is the result of His Will, even when it appears to be bad. This teaches us that all that occurs is actually for the good, although we may not be capable of understanding how.

Those who believe in multiple gods, and also those who deny His existence entirely, frequently point to the apparent contradictions of the world. We see many conflicts in the world, both in the natural world - as in the struggles between different species - and in human civilization. These apparent conflicts between good and evil, light and darkness, human society and natural forces, are seen by these people as contradicting the idea that one God could be the Cause of all of creation. The Torah teaches us that HaShem does control all of Creation and even events that seem to be bad are for a good reason. Someday all these questions will be answered and everyone in the world will recognize that HaShem is the One True Ruler over the entire universe.

Despite the apparent simplicity of this concept of the Unity of God, this concept actually raises many difficult questions about our understanding of HaShem. These questions are discussed at great length by many of the great Jewish philosophers and thinkers. Ultimately, however, the difficulty is that we cannot actually comprehend the idea of absolute unity. Rabbi Moshe Chaim Luzzatto (1707-1746), one of the greatest Jewish thinkers of all time, writes:

It is necessary to know that God’s existence is absolutely simple, without combinations or additions of any kind. All perfections are found in Him in a perfectly simple manner…. In truth, this is a concept that is very far from our ability to grasp and imagine, there is almost no way to express it clearly and explain it in words, because our minds can only grasp those things which are bound by the laws of nature created by HaShem.

Derech Hashem I:1:5