Answer
Yahwism can refer to a couple different things. One use of the term relates to the JEDP theory—Yahwism, in that context, is the use of the name Yahweh in the Pentateuch. The Yahwist (or Jawist) is the J of JEDP—the supposed earliest contributor to the Pentateuch. The JEDP theory has no basis in reality and is an attempt by liberal scholars to disprove the authority of the Bible.
The other use of the term Yahwism, and the focus of this article, is as the name of the Tanakh-based monotheism of the Israelites, as distinct from the polytheism of the surrounding nations. The name comes from the covenant name for God, Yahweh (YHWH), and it is the only name for God that modern Yahwism accepts as biblical. Yahwists reject the names God, Jehovah, and Lord as being pagan in origin. They call Jesus “Yahshua.”
Modern Yahwism holds the Hebrew Bible to be the sole authoritative book. Yahwism also accepts the Synoptic Gospels and the epistle of James (since they see those books as supporting the Hebrew Bible). Yahwists reject the Gospel of John and the writings of Paul (a Pharisee who was not included in the original twelve disciples), believing that those books represent human attempts to add to Yahweh’s Word. They also reject the Talmud and all rabbinical additions to the Tanakh.
Yahwists sometimes refer to Yahwism as “Israelism” and to themselves as “True Israelites.” Anyone who calls God by a name other than “Yahweh” (such as “God”) or who accepts the oral tradition of the Jews is not a True Israelite and has bought into a false religion. According to Yahwism, Christianity and most versions of Judaism are false religions.
Yahwism rejects the doctrine of the Trinity, teaching that Yahweh cannot be “divided” into different persons or beings. Of course, saying that God is “divided” into Father, Son, and Spirit misrepresents Trinitarian doctrine, but that is the wording used by Yahwists. Yahwism teaches that Yahshua (Jesus) honored the Torah and was a true teacher of Yahwism, but He was not divine in any way and did not die for anyone’s sins. Yahwism teaches that salvation only comes through keeping Yahweh’s covenant in the Torah faithfully.
Yahwism relies on a works-based salvation: if one returns to a proper keeping of Yahweh’s commandments, he can enter into the covenant with Israel, become a “True Israelite,” and be made an heir of eternal life. Even then, Yahwists do no keep the whole Law—they only observe four of the seven feasts of the Lord, they do not offer sacrifices, etc. They deny the fact of progressive revelation and that Jesus is both Lord and Savior: “In the past God spoke to our ancestors through the prophets at many times and in various ways, but in these last days he has spoken to us by his Son, whom he appointed heir of all things, and through whom also he made the universe. The Son is the radiance of God’s glory and the exact representation of his being, sustaining all things by his powerful word. After he had provided purification for sins, he sat down at the right hand of the Majesty in heaven” (Hebrews 1:1–3).