Mary enters the house and looks into the living room. A familiar appearance greets her from her husband’s chair. She thinks, “My husband is sitting in the living room,” and then walks into the den. But Mary misidentified the man in the chair. [Perhaps she only saw the back of his head.] It’s not her husband, but his brother, whom she had no reason to think was even in the country. However, her husband was seated along the opposite wall of the living room, out of Mary’s sight, dozing in a different chair.
Would you say that Mary knew her husband was in the living room or, because she was mistaken about the evidence, was she merely lucky?
This is an example of a Gettier Problem: a class of philosophical situations designed to show that the classic definition of knowledge as justified, true belief falls short.
Mary believes her husband is in the living room, it is true that her husband is in the living room, and we would normally take the testimony of our own eyes as adequate justification for such a belief. Yet, considering the fact that her justification was completely mistaken, she seems more lucky than knowledgeable.
Philosophers have proposed many ways to either rescue or amend the “justified, true belief” definition of knowledge. To me, it’s pretty simple: what we think of as justification is almost always probabilistic, not absolute, so our knowledge is, too.
If a lawyer had been grilling Mary, she would have had to admit that, yes, there was a small probability that her husband’s brother was the one in the chair, or that someone had decided to prank her by putting a model of her husband in his chair, or even that she hadn’t looked closely enough and what she thought was the back of her husband’s head might have been their rust-colored pillow out of place.
Those are all low-probability events, but they do happen.
When we are in the middle of a Gettier-type situation, we are by definition unaware of it, so it’s appropriate to stay humble about how much we know, even based on good evidence.
Here’s a Gettier situation that happened to me decades ago but has haunted me ever since. I was driving down a suburban street at the speed limit of 35 miles per hour. Following close behind me was a station wagon with a very impatient driver. She was honking at me. “What a jerk,” I thought. “I’m not going to speed up. I’m going plenty fast already. I’m not going to pull over, either.” Based on abundant evidence, I had concluded that she was an obnoxious driver, and I was right.
This was a no-passing zone, so she stayed behind me until there were two lanes in our direction. As she finally passed me, I glared into her car and saw she had a male passenger about her age slumped in the front seat with his head back. I then realized she was probably on her way to the nearby hospital with her husband who had suffered a heart attack.
I hope the man survived, but I will never know. What I do know is that we can be right based on good evidence, but tragically mistaken at the same time.