Think about how this kind of reasoning relates to the intelligent design and evolution debate.
Even if you don’t know how to define life, you know it when you see it. But how?
Consider an analogy. Imagine you have gone to visit the circular pattern of great stones on the Salisbury Plain in England known as Stonehenge.
Given its widespread popularity and acceptance you might not have realized that the so-called RNA World hypothesis suffers from some dramatic problems.
“Not exactly proof” of extraterrestrial life, they say? It’s not a “proof” at all.