Jordan Peterson is making an excellent point here, one that will be instantly recognizable to experienced attorneys. Every time a question is asked, various concepts are embedded in the question. In this video, the question considered is "Do you believe in God?" Anyone who answers this without questioning the meaning of God is committing intellectual malpractice.

Einstein believed in "God," but that "God" was nothing like the God of the Abrahamic religions. Einstein said, Einstein said, “I believe in Spinoza’s God, who reveals himself in the lawful harmony of all that exists, but not in a God who concerns himself with the fate and the doings of mankind.” Now consider typical understandings of "God," the understandings of most religious believers.

Consider these two dramatically different meanings of "God.  Now consider how different these two conversations would be! To proceed with this conversation about "God" without first coming to a common understanding of the meaning of "God" would amount to two ships passing in the night, even though it might, for awhile at least, seem to be a meaningful conversation. It would be, in fact, a waste of time.

There are limits to the power of words, of course. Meaning is ultimately squishy, no matter how hard we try to pin down the meanings of words. There is no perfect etched in stone definition to most concepts, so we need to proceed in the face of somewhat (or wildly) imprecise definitions or else we can't ever have these conversations.  On the other hand, proceeding with a conversation without any effort to make sure that we all know what we are talking about, is folly.