The strongest and most powerful way to apply all of the previous steps is in this one: Act as if it is already true. Act like the person you want to be. Act as if you already have everything you want. Act as if everything you need has already been provided. This is how you finally accept your manifestation and allow yourself to receive it from the universe.
People living today have the same access to the original creators' texts online as people in 1880 had in printed books. It's exactly the same material. You're essentially arguing against yourself because asserting that no one knows for sure about it would have to apply to the people in 1880 as well. Your argument is an appeal to ignorance, which is a logical fallacy. The text in the creators' books is precisely the data he's referring to, a intellectual creation that has absolutely no scientific basis.
It's curious that people who believe in a LOA are critical of those who don't and believe them to be close-minded. I have presented a lot of new data such as the erroneous science and the data showing that acting as though you had already accomplished your goals was detrimental to you doing so. Yet, LOA proponents do not look at this with an open mind and reconsider their belief system. In this way LOA is akin to a faith-based religion, except that religious beliefs can't be disproven.