I once spoke to a professor who said that Krsna consciousness appears to be a combination of logic and sastra. I asked Prabhupada about this and he replied to me as follows:

“Concerning our use of analogy. We do not bring in imperfect analogy, but we follow the instructions of the sastra strictly. Our authority is on the basis of sastra, not analogy… We give analogy for the general mass of people who have no faith in sastra. Analogy is not proof, sastra is proof. Foolish people cannot understand or accept, so we use analogy. The conclusion is not drawn from the analogy but from the sastra. We don’t use a combination of logic and authority, we use authority. The logic of using analogy is called in sastra, ‘sakha chandra nyaya.’ It is easier to focus on the moon through the branches of a tree.” (Letter 75.10.21)

From Satsvarupa das Goswami’s Vyasa-puja offering to Srila Prabhupada, 2020