The foundations of Judaism are compiled by Maimonides.

Also known as the RaMBaM, an acronym for Rabbi Moshe ben Maimon, he wrote a code of Jewish law called the Mishne Torah and many other commentaries on Torah. He explains that there are 13 Principles of Judaism :

1. That the Holy One, Blessed Be He exists & supervises
2. & that He is One
3. & that He has no body & no likeness of a body
4. & He was before anything from before
5. & that there is no worship except to Him
6. & He knows the thoughts of people
7. & the prophesy of Moses our teacher is true
8. & that he (Moses) is the master of all prophets
9. & that the Torah was given from Heaven
10. & that it [the Torah] will not change at any time, G-d forbid
11. & that G-d punishes evil & greatly rewards the good
12. & that the king Messiah will come
13. & that the dead will be resurrected in the future.

to decide to believe in Judaism you should answer the following:

1) Does it make more sense that G-d exists or not?
2) Did G-d Give a Law to People?
3) What is that Law?
4) Did G-d Change His Mind?

Here are answers:
1) Yes. It doesn’t make sense that the world came about by randomness.
2) Yes, A company wouldn’t offer a product without user instructions – even clothes have washing instructions.
3) The Torah is the only law that was given by G-d to an entire nation of millions of witnesses in the entire history of the world. Of the thousands of religions that exist, no other religion claims this fact. Almost all people agree that the Torah / the 5 Books of Moses was given by G-d to the Jewish People.
4) G-d said he will not abandon the covenant with the Jewish people. Also, does it make sense, that G-d, Omniscient and Omnipotent, with knowledge of all the past, present and future will change his mind. G-d knows all and knew that the Jews would keep the Torah till today. A person bets to win not to lose. G-d, knowing the past, present and future, put “His money” on the team (ie, the Jews) that he knew was going to win.

Abraham taught the world that anything that has a weakness cannot be god. Anything that can be destroyed, or can die – anything physical or spiritual – like an object, animal, tree or person – cannot be God.

The 13 Principles
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Our Free Happiness Card Contains the 13 Principles