G-d is the L-rd, there is no other beside him.(Dvarim / Deut. 4:35)

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You have been shown, so that you know that G-d is the L-rd, there is no other beside him.
(Dvarim / Deut. 4:35)

In the commentary of Kli Yakar to Shmot /Exodus 7:17, it is written regarding the ten plagues, regarding the last set of 4 plagues [which the Passover Hagadda] called by the Abbreviation B.A.CH.B., Rabbi Yitzchak Abarbanel explained that they came to verify the ability of G-d, may he be blessed. But it appears to me that Pharoah claimed that there were 2 authorities; therefore it was stated in the first plague of this set B.A.CH.B. "in order that you know that there is none like me on Earth". That is to say, there is no other beside him, May G-d Be Blessed, namely, no other authority. And so it appears to me that also according to the commentaries of the Netziv and the Malbim to Dvarim / Deuteronomy 4:35, one should explain "there is no other beside him" as a negation of the concept of 2 authorities [each one expresses this idea in his own style].
   It is implied to me from Rashi's commentary to this verse [Dvarim / Deut. 4:35] that he agreed that the intent of "there is no other beside him" is to negate the concept of 2 authorities. However, in his opinion, the proof that "there is no other beside him", is not from the ten plagues, but rather from the revelation of the Torah to Israel at Mount Sinai. As it is written there: "that when the Holy One Blessed Be He gave the Torah, he opened up for them, the seven heavens and just as he tore open the upper realms so too did he tear open the lower realms and they saw that he is single, therefore it was stated you have been shown, so that you know".
   From the words of the Talmud, tractate Chulin page 7, it is implied that the expression "there is no other beside him", comes to inform us, that if we have merits, the system or order of sorcery that G-d himself produced to deny his heavenly entourage, will not be able to harm; just as the system of sorcery did not harm, at the time of the ten plagues, and at the time of the sorcerer, Bilaam. Now here I will quote:
   "There is no other beside him", Rabbi Chanina said, even sorcery "{end of quote}.
   The Talmud afterwards explained, that there was a witch that tried to perform witchcraft against Rabbi Chanina. And he responded, that the witchcraft did not succeed against him, "there is no other beside him". The Talmud asked, behold, did not Rabbi Yochanan say, that these matters are called witchcraft {or sorcery}because [the name for these things in Hebrew imply that] they deny his heavenly entourage? {That is to say, that it is implied that witchcraft/sorcery do have the ability to cause harm}. The Talmud answers, Rabbi Chanina is different, for his merit is great.
   In Rambam's opinion as recorded in Hilchot Yesodei Torah chapter 1, halachas 3 and 4, the purpose {in summary} of "there is no other beside him" is to come and negate the Greek notion, that the world or that matter is eternal. And the Rambam established "that all those that are present need him, and He, Blessed Be He, does not need them nor even one of them, therefore his truth is not like the truth of one of them". {The commentary of Rambam La'am explains: the existence of the rest of the things that exist is not of absolute necessity, for they are dependent upon others, namely, by the reason that caused them to come to be - therefore they are just possible existence: it is possible that they endure and it is possible that they do not endure; however the first presence which is before every other thing that doesn't have a cause for its existence, this existence is a necessity...}
   Now one should comment in the Hilchot Yesodei Hatorah, Rambam did not go to the trouble to explain, what did the nation of Israel, see ("you have been shown, so that you know") that proved that there is no eternal matter which exists outside of the Holy One Blessed Be He ("there is no other beside him").
for more on this general subject see http://www.vilnagaon.org/monotheism.htm