In the early 20th century there was a popular movement known as verificationism. This school of thought said that in order for a statement or word to be meaningful it had to be verified by the 5 senses. (Perceptions, Observations, Experiences).
This posed a huge problem for religious language about God because “God” and “God is Love”, could not be verified by the 5 senses. Therefore, such words were meaningless.
The problem for verificationism is that it was too restrictive. There are many things not testable by the 5 senses. Ethical judgments, logical first principles, metaphysical claims, etc.
Even worse, verificationism itself was self-defeating. The principle couldn’t be tested by the 5 senses. So it was either meaningless or a principle that was baseless.