Who says?

We've discussed the basic requirements for knowledge. If you remember, knowledge is obtained when you have a belief justified by real-world truth. We even discussed two schools of thought about when you do and don't have that real-world justification. What we didn't cover is the criteria under which we gain that justification.

So, what should we consider the proper conditions under which we attain justification for knowledge? Consider the following story (with added drama for effect). You are the sonar operator on a submarine. You are currently engaged with an enemy submarine and you have one torpedo left. It's up to you to save your crewmates by finding the other sub before it finds you. Suddenly, on the screen, a blip appears. The other sub! You relay the coordinates to the torpedo room and they use the last missile to sink the enemy into a watery abyss. Congratulations! You lived to scuttle another day.

Now, I'd like to pose a question. Did you know the other submarine was there? Of course you did. The sonar showed the blip and the torpedo hit the other submarine, which was right where the sonar told you it would be. You had knowledge (the other sub's location) based on a justified belief (the sonar blip) which came from truth (the enemy submarine's location).

Now, let me rewind the clock and look behind the curtain of this scenario. What if I told you that you had a spy on-board your boat? His mission was to tamper with the sonar system in order to make it appear that there was a submarine where one did not exist, thereby making your torpedoes wildly inaccurate. Now, when you look at the blip on screen, what do you see? You see a blip where (unbeknownst to you) no blip should be. However, you reasoned that there is a submarine where there actually wasn't. "But wait! Then, what did we hit?!" you ask. Well, in some strange twist of fate, the enemy submarine just happened to appear in the exact spot the faulty sonar told you it would be, and therefore, you hit it. So, can you say that you had knowledge of the submarine's location?

This is what's referred to as a "Gettier" case, after Edmund Gettier. The idea is that you can have the "justified belief" mentioned last time and still not have real knowledge. You do not have knowledge because your justified belief did not reflect the real world circumstances. This is also called reasoning from a false premise. You can reason correctly based on false evidence but still have the outcome that resembles knowledge.

So, when considering what you know and how you know it, take a step back and consider your sources.