So does any religion that “worships” a monotheistic “highest power” – in whatever way that is conceived and by whatever ritual is the prescribed one – believe in the same God? I would be a bit concerned about the principle this establishes.
Let’s take Pharaoh Akhenaten (Amenhotep IV, 1364-1347 B.C.). According to this pharaoh, Aten (God) created himself (akin to the theistic idea of existing a se without the benefit of philosophical clarity) and illuminated the world of the living and the dead. Akhenaten, was uncompromising in his monotheism. He made Aten the supreme and only state God, symbolized by a disk with rays ending in hands for different ministeries. Worship of all other gods was abolished, their images destroyed, names excised, temples left abandoned, and all tributes to them confiscated. The plural term for deities was no longer used.
Was this Pharaoh worshiping God? I think you would have to say he was if you hold that Mohammed was.
I would suggest that he was more likely to actually have been worshiping God than Mohammed was, given the source or inspiration for his beliefs and actions seemed directly from his heart and mind rather than through external stimulus or base desires and ambitions. His actions also seem consistent with inspiration by the same God we are familiar with from the OT.
Mohammed’s “inspiration” is somewhat more dubious and appears to have been more akin to projecting his own aspirations, desires and personality traits onto the entire universe to make out of them, collectively, the highest and only supreme “god” controlling the universe. This “projection” then appears to turn around, take on a life of its own and directs Mohammed to carry out those aspirations and aims in the world around him under the guise of the one omnipotent being who controls the entire world and desires complete submission from it.
Mohammed’s “God” can be explained psychologically in terms of Mohammed’s own personality being “deified” and imposed on the world as from one omnipotent “God” to rule over it, whereas though Akhenaton might be understood this way, it seems less likely because a Pharaoh in Egypt already enjoyed that kind of power over his subjects, so there wouldn’t be any psychological need or motive to reduce the pantheon of Egyptian gods to one. His monotheism would seem less well-explained in terms of power-based ambition and, because of that, seems more authentic.
Now I might agree that many Muslims, as a matter of fact, worship the same God as Christians and Jews in their own way, and have perhaps even direct or intimate knowledge of God via natural grace, but I remain dubious that the god experienced by and portrayed by Mohammed is that God. I would also suggest that one way of telling regarding who is worshiping God and who is not, is by the actions that follow from their alleged knowledge of that God.
I would claim the same thing about some Christians, who by their actions betray God or undermine his image and plan, and therefore cannot know, love or worship the real God of Abraham and the Apostles.