Elementary spiritual author

Hello everyone,

I come from a buddhist training and tradition and I wonder if anyone here kindly could refer me to the author who first presented the idea quoted idea, or to someone who is a very prominent spokesperson for it?

Universal Religion: Since all is God, then only one reality exists, and all religions are simply different paths to that ultimate reality. The universal religion can be visualized as a mountain, with many sadhanas (spiritual paths) to the summit. Some are hard; others easy. There is no one correct path. All paths eventually reach the top. They anticipate that a new universal religion which contains elements of all current faiths will evolve and become generally accepted worldwide.

Best regards, and thank you for reading!