Replies

Their revelation was not as full as ours is, but it was "enough" to correctly believe in the one true God

Their idea of God is nothing like ours. We can all say there is one God, no matter what our idea of Him, but only through Christ do we believe in one true God. It's not God that is faulty but human idea of God that is. Thus, the Muslims idea of Allah is not what we know of God through Christ; otherwise we would have to say that Muslims believe in one true God.

By the same token, the Hindus believe in one God (contrary to popular opinion). In fact, Hinduism is the oldest written religion in the world, predating Moses. Brahman is described as

"unchanging, infinite, immanent, and transcendent reality which is the Divine Ground of all matter, energy, time, space, being, and everything beyond in this universe."
"This Supreme Cosmic Spirit or Absolute Reality called Brahman is said to be eternal, genderless, omnipotent, omniscient, and omnipresent, and ultimately indescribable in the human language. It can be at best described as infinite Being, infinite Consciousness and infinite Bliss. Brahman is regarded as the source and essence of the material universe. It is pure being."

by the Hindus.

The plain fact is the Jewish idea of God of Abraham is ontologically different from the Christian God. Otherwise, we would all be Jews. We can speculate whether the OT righteous would have recognized Christ as true God, but we can't prove it or disprove it. therefore we cannot with any certainty say that they were true believers.

Their idea of God is nothing like ours. We can all say there is one God, no matter what our idea of Him, but only through Christ do we believe in one true God.

Yes, only through Christ. But Christ was all over the OT and the righteous recognized Him. We know from John 6:46, and 1:18 that no one has seen the Father. However, there are several stories in the OT of people "seeing" God. So, Who could that be? Jesus, of course.

Here is a list of sightings: Hagar [Gen 16:7-13], Abraham [Gen 18-19:1], Jacob [Genesis 32:28--see Hosea 12:3-5], Moses [Exodus 33:11], Joshua [Joshua 5:13-6:2], Gideon [Judges 6:11-23], Manoah [Judges 13:2-22], Isaiah [Isaiah 6:5] Job [Job 42:5]. I think you are making the assumption that since no one had the NT in his hands in the OT, that they could not have believed in Christ. That just isn't so. Not only was there tons of prophecy about His Incarnation, He was actually very active in the OT. Jesus Himself says that the OT testifies about Him.