Answer: Repeatable results, just as in any science, the reproduction of a result by a person who is able to check it on himself.
Kabbalah, like any science, needs verification. Moreover, it welcomes such checks tests that are repeated by renowned and respected Kabbalists. They review the research and approve the publication of a relevant book. Later others can also use this book.
From KabTV’s “Fundamentals of Kabbalah” 11/11/18