Notes for 3/6/2026

  

3/6/2026

[Philosophy Club every Monday, 4-5 pm, in the Buchtel College of Arts and Sciences room 436 ("The Cave")]

[Bioethics Club: Mondays from 5:30pm-6:30pm in Leigh Hall 408]

 

What is one thing you’d have to see to believe?

 

Suppose we accept that inductive inference is reliable (as it seems we should).

 

That is, we can, in good conscience, accept that:

     The future will continue to resemble the past.

 

 

Nelson Goodman suggests that we still have a problem.

 

 

Imagine that one day space aliens land on Earth in search of emeralds.

 

Because emeralds have the most beautiful color – “grue”.

 

In the alien language, “grue” means “green if observed before 1/1/2027 and blue thereafter.”

 

They also like sapphires, because sapphires are “bleen” – blue if observed prior to 1/1/2027 and green thereafter.

 

 

As an Earthling, you believe that all emeralds are green, and all sapphires are blue.

 

The alien believes that all emeralds are grue and all sapphires are bleen.

 

But (since 1/1/2027 isn’t here yet) you and the alien have exactly the same inductive evidence for the claims:

(A) All emeralds are green.

(B) All emeralds are grue.

 

 

You say, “All the emeralds I’ve observed in the past have been green, so inductive reasoning tells me that all the emeralds I observe in the future (including after 1/1/2027) will also be green.”

 

The alien says, “All the emeralds I’ve observed in the past have been grue, so inductive reasoning tells me that all the emeralds I observe in the future (including after 1/1/2027) will also be grue.”

 

You say, “But that’s crazy, because if an emerald is grue, it will change color from green to blue on 1/1/2027.”

 

The alien responds, “No, you’re the one who is crazy, because if an emerald is green, it will change color from grue to bleen on 1/1/2027.”

 

 

Goodman’s point is that the rule “the future will resemble the past” doesn’t help unless we can answer the question of what, exactly, it means for the future to resemble the past.

 

 

If all emeralds really are grue, then if emeralds all change from green to blue on 1/1/2027, then the future will turn out to have resembled the past in respect of grue -ness, but if they don’t change from green to blue on 1/1/2027, then the future will turn out to have resembled the past in respect of green -ness.

 

We DEFINE “grue” in terms of a change.

Aliens define “green” in terms of a change.

 

 

Whether the future resembles the past or not is not just a function of inductive reasoning, but also of the concepts we apply to things in the first place.

 

We think the concepts we use are “correct” and the concepts the alien uses are “weird.” But what determines that this is true?

 

Most people think the grue problem is just an intellectual curiosity. But it actually has important and far-reaching implications because it forces us to ask whether our concepts are the only or right ones.

How do we know our concepts are the best model for reality?

 

Representationalism: We don’t perceive the world directly. Rather, our perceptions involve filters from our senses, but also from our language, concepts, …