Knowing vs. Articulating
At one point or another, we have probably all come across a person who claims to possess a type of arcane knowledge that is difficult to articulate: a vague dread that comes before a natural disaster, a strange love of something or someone, a mystical revelation.
You might ask people possessed of such knowledge a question about it and they might answer, "I can't explain it; I just know it."
This type of argument is very thin when the question is "What is your control group?" or "What makes x a reasonable assumption?" To such questions, we need to be able to articulate concise answers that others understand. If we cannot articulate an answer, we can safely assume that we do not know it.
So, don't be caught short! Practice articulating 1-sentence answers to questions from others till you know your work well enough to explain it to a duck.
Blog Post: Varanya Chaubey Image: Thomas Jones [Public domain], via Wikimedia Commons