In the beginning, God. In the end, God.
Li's doctrinal scheme was simply Li's folk understanding of the Buddhist notion of nirvana. Li did not believe in an eternal soul that was separable from nature. Instead, he believed that every man's soul would be destroyed without exception. Man had a choice whether to allow this destruction to lead him to hell or to lead to the empty hulk of his destroyed soul returning to God. The soul becomes nothing, the soul joins God. This is nirvana and bears no resemblance to the salvation in Christianity.
Further, God too follows the same process. God's nature is not immutable and eternal. Since man becomes God, God undergoes the process while man does. This means that in effect God is nothing more than the "All" of Buddhism. Thus since Lee's scheme requires that God is both Creator and the created, the individual and the all, Lee taught pantheism.
Moreover, Li taught that the process of soul-destruction and returning to God involved mechanical processes whereby definite proportions of God would replace the man's soul, destroy it and then return to itself, Lee was establishing materialistic mechanisms for the spiritual realm. This reduced the spiritual to the material.
In short, Li was a pantheistic materialism, which is essentially what Buddhism is. Naturally did not possess the education to elucidate this, but on the other hand he was selling his understanding of the Chinese folk Buddhism he was raised under in China as Christianity to a Christian culture; he would not have sold this successfully were he up front about it. Be that as it may, Li's methods of emptying the mind with meaningless words are traits specific to Buddhism of the Far East and Li's soul-destruction = the nothingness of nirvana.