system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the idiom "the exception that proves the rule" make any sense?

How can an exception from something prove a rule? Like if i don't blink when i sneeze, how am i in any way proving that people as a rule in fact do blink when they sneeze?
gpt
The expression "the exception that proves the rule" is legal concept (*exceptio probat regulam*), and is often misunderstood. What it actual means is that you can *infer* a law when an *opposite* and *explicit* law is present. The classic example is a sign that says, "No Parking between 8am - 5pm." The explicit law is that the you can't park there during that time period. The implicit law—the law that is not directly mentioned—is that you *can* park there anything *outside* 8am - 5pm. The signs does not say that you can park there, but the principle of *exceptio probat regulam* implies that you can. Similarly, let's say that on the street, one spot has signs that say you cannot park there. This implies that you can park everywhere else on that street. That one spot is the exception, and so the rest of the street is the rule.