The Missing Shade of Blue facts for kids
The Missing Shade of Blue is a famous example from the Scottish philosopher David Hume. He used it to explore a big question: Can our minds create an idea of something we've never experienced with our senses? This idea seems to go against what Hume usually taught, which makes it a puzzle for philosophers.
Contents
What's the Big Question About Ideas?
David Hume wrote two important books, A Treatise of Human Nature and An Enquiry Concerning Human Understanding. In these books, he said that everything we think or feel in our minds can be put into two groups: 'Impressions' or 'Ideas'.
- Impressions are our direct experiences, like seeing a bright red apple or feeling the warmth of the sun. They are strong and vivid.
- Ideas are what we think about later, like remembering the red apple or imagining the sun. They are less vivid than impressions.
Hume believed that all our ideas come from our impressions. He said, "Every idea we look at is a copy of a similar impression." He even challenged anyone who disagreed to find an idea that didn't come from an impression.
But then, just a few paragraphs later, Hume himself presented a possible exception! This is where the problem of the missing shade of blue comes in.
Hume asked us to imagine a person who has seen many colors for thirty years. This person knows all shades of blue, except for one specific shade they have never seen. Now, imagine all the shades of blue, from darkest to lightest, are placed in front of this person, but with a gap where that one missing shade should be.
Hume then asked: Can this person, using their imagination, create the idea of that missing shade of blue, even though they've never seen it? He thought that most people would say "yes."
This example seems to show that sometimes, simple ideas might not always come directly from impressions. However, Hume thought this was a very unusual case and not important enough to change his main rule about ideas.
How Philosophers Respond to the Puzzle
Some philosophers think Hume was wrong to just ignore this example. Pritchard felt that Hume should have changed his whole theory because of it. He thought it was bold of Hume to dismiss something that seemed to go against his main point.
Other philosophers are more understanding of Hume's view. Jenkins, for example, suggests that Hume's main point was that you can't have ideas without some kind of sensory experience. He argues that the missing shade of blue still depends on having seen other shades of blue. It's not like the idea just appeared out of nowhere. It just shows that our minds might be a bit more creative than Hume first thought.
Some people even argue that the problem is bigger than Hume realized. Alexander Broadie pointed out that if you can imagine a missing shade of blue, you could probably imagine missing shades of other colors too. And why stop at colors? Maybe you could imagine a missing sound, taste, or smell!
However, others like Williams say that Hume probably knew this. Hume himself mentioned both sounds and colors at the start of his example. When he said "for instance" about the blue shade, it meant he could have picked any other example. So, when Hume called the example "singular," he likely meant the type of exception it was, not just that specific blue shade.
Hume also described colors as if they were separate, distinct ideas. But in reality, colors flow smoothly into each other, forming a continuum. Philosopher Fogelin suggests that Hume might have been thinking about the ideas of colors, not the colors themselves. He might have believed that if two ideas are different, you must be able to tell them apart.
Possible Ways to Solve the Puzzle
A good solution to this puzzle would need to:
- Agree that Hume saw this as a real exception.
- Understand why Hume included the example.
- Fit well with Hume's other ideas about how we gain knowledge.
Here are some ways philosophers have tried to solve the problem:
Mental Mixing of Ideas
One idea, called "mental mixing," suggests that our minds can mix ideas of colors, much like you mix paints to get new shades. So, if you've seen light blue and dark blue, your mind could "mix" them to imagine a shade in between.
But it's not clear if our minds actually work this way. And if they do, why would it only apply to very similar ideas? If we could mix any ideas, it might lead to all sorts of strange ideas that don't come from experience, which Hume wouldn't like.
Colors as Complex Ideas
Another idea is that colors themselves might be "complex ideas." Hume said that we can combine, rearrange, make bigger, or make smaller the things our senses give us. For example, our idea of God comes from taking human qualities like goodness and wisdom and making them "without limit."
However, Hume clearly said that "simple ideas" cannot be broken down into parts. He used the example of an apple's color, taste, and smell. They are all together in the apple, but you can tell them apart. He thought a single color was a simple idea, meaning it couldn't be divided. So, this solution doesn't quite fit with Hume's own definitions.
It Doesn't Change Hume's Main Point
Perhaps Hume wasn't too worried about the missing shade of blue because it didn't challenge his main goal. Hume's main goal was to check if philosophical terms had real meaning. He said that if you suspect a term has no meaning, you should ask: "Where did this idea come from?" If you can't find an impression it came from, then the term might be meaningless.
The missing shade of blue example does contradict the idea that all simple ideas come from simple impressions. But some argue that this specific contradiction wasn't Hume's biggest concern.
The Exception Really Is Unique
Fogelin argues that the missing shade of blue is a true exception that can be safely ignored. He says that colors (and sounds, tastes, etc.) can be organized in a very structured way, like a color wheel. Hume allowed that simple ideas can be similar to each other without sharing any separate parts. For example, blue and green are different simple ideas, but they are more alike than blue and scarlet.
This ability to see similarities allows us to arrange shades of blue in order. It also helps us notice a gap where a shade is missing. So, being able to fill a gap in a known color sequence is different from creating a completely new idea from nothing. The idea of the missing shade still depends on having seen other shades of blue.
The challenge with this view is proving that this exception is truly limited. If it's not, it could weaken Hume's general rule that ideas depend on impressions.
Hume Needed an Exception
Some philosophers, like Nelson, suggest a fascinating possibility: What if Hume included the missing shade of blue on purpose? Later in his work, Hume divides all knowledge into two types:
- Relations of Ideas: These are certain truths, like math (2+2=4). They don't tell us anything about the real world.
- Matters of Fact: These are about the world, like "the sun will rise tomorrow." The opposite of a matter of fact is always possible (the sun might not rise).
Hume's claim that "all our ideas are copies of our impressions" is a matter of fact. If it's a matter of fact, then it must be logically possible for it to be false. The missing shade of blue example, even if it's just a hypothetical possibility, shows that it's possible for an idea to arise without a direct impression. This would make Hume's claim about ideas a true "matter of fact."
However, what's needed for a matter of fact is logical possibility, not practical possibility. So, Hume didn't necessarily need such a detailed example. He could have just said that we might have been made differently.
One Exception Doesn't Change the Odds
Hume believed that when we think about "matters of fact," we use a kind of probabilistic logic. This means we weigh all the evidence for and against something to decide how likely it is. He said that the probability of a factual statement is found by looking at all the evidence.
Since Hume's idea that "all simple ideas come from simple impressions" is a matter of fact, we can think of it in terms of probability. Almost all other experiences support his idea. So, the "missing shade of blue" example, being just one exception, would have a very small effect on the overall probability of his theory. That's why Hume might have said it was "scarcely worth our observing."
However, Hume also called the missing shade of blue a "proof" that simple ideas are not always from impressions. In another section, he defined "proof" as an argument from experience that "leaves no room for doubt." If he used the word "proof" consistently, then the missing shade of blue should have a much bigger impact on his theory's probability, perhaps even making it seem doubtful.
See also
- Color vision
- Mary's room
- New riddle of induction
