Nagel--some prelims

Nagel-Public Education and ID

ID = intelligent design

Technically speaking there are two different versions of ID. There is a biological version and a cosmological version. The bio version is way more controversial than the cosmo version. According to the bio version (at minimum), there are bio organisms or structures that cannot be explained via natural selection and random mutation. Instead, such structures are better explained via some kind of intentional design. According to the cosmo version of ID, there are cosmological features (features that seem to characterize the entire universe) that are best explained by intentional design. Nagel's piece is only concerned with bio ID. So, in this post, ID refers to bio ID. 

IC = irreducible complexity

IC is one of the main pieces of data or evidence that ID advocates use to defend their claims. At a minimum, A system is IC just in case the function of that system requires the presence of all of the parts of that system.  For example, what parts are necessary for a clock to do what it does? Perhaps there must be a face of some sort, some kind of representation of numbers, and some moving parts. If you take away any of those things then you no longer have a working (a functional) clock. Hence, a clock exhibits IC. Of course, most clocks can lose a lot of their parts and still function (e.g. they can change color, they can change their shape, they can change their size, etc). So, when we talk of IC systems we are talking about the most basic parts needed for the thing to carry out its function. 

Here's Nagel:

“ID … is best interpreted not as an argument for the existence of God, but as a claim about what it is reasonable to believe about biological evolution if one independently holds a belief in God that is consistent both with the empirical facts about nature that have been established by observation, and with the acceptance of general standards of scientific evidence” (188).

So, Nagel takes ID to be some belief about biology that is conditional on theism.  Given theism, such-and-such bio features are to be expected.  I am not sure that IDers would agree with this, but perhaps they should.

A proposition p is conditional on another proposition q just in case, the likelihood of p is increased given the truth of q.  So, Nagel is claiming that IDers think that ID is likely given the truth of theism. Assume the truth of theism and ID is likely.  

To write 'p is conditional on q' we write: p/q (this says 'p given q' or 'p on the assumption of q'). 

We can represent these kinds of claims using probability. If I roll a normal and fair die what is the probability that it comes up a 4? The answer is: 1/6. We can write this as:

P(die is 4/die is normal and fair) = 1/6

This says: The probability of a die coming up 4 is 1/6

So, we can represent Nagel's claim as follows:

P(ID or IC—irreducible complexity/Theism) is high

This says: the probability of ID or IC, given (assuming) the truth of theism is high

Or perhaps Nagel is saying this:

P(ID or IC/Theism) > P(ID or IC/~Theism)

This says: the probability of ID or IC, given theism is greater than the probability of ID or IC, given the denial of theism.

More simply: Assuming that theism is true, things like the complexity of organisms that appear designed are not surprising.  But assuming the denial of theism such things are surprising.  

More simply still: suppose we travel to Mars with the following knowledge: there has never been an intelligent being on or near Mars.  Now suppose that we discover something that looks like a watch.  What should we conclude? Given our knowledge, we should conclude that the thing that looks like a watch is NOT a product of intelligent design.  Let’s start over.  Suppose we travel to Mars with the following knowledge: there have been intelligent beings on or near Mars.  Now suppose we discover something that looks like a watch.  What should we conclude? Given our knowledge, we should conclude that the thing that looks like a watch IS a product of intelligent design.  

So, our background, metaphysical assumptions are doing a lot of work in how we interpret the world.  That’s Nagel’s main point.  

So we get the following argument:

1.     P(IC/ID) is high or at least P(IC/ID) > P(IC/~ID)

2.     P(ID/Theism) is high or at least P(ID/Theism) > P(ID/~Theism)

3.     Hence, P(IC/Theism) is high or at least P(IC/Theism) > P(IC/~Theism)

This tells us that IC events are not surprising given the truth of theism and are surprising given the truth of atheism.  It does not tell us that theism is likely given IC event.  So we are starting with theism and seeing what follows, what we would expect the world to be like.  

I think a lot of IDers think of their work differently (perhaps Nagel is right though that they should not think of their work differently).  They see themselves as simply discovering certain types of phenomena, namely IC phenomena, and showing that such phenomena makes ID likely.  In other words, I think some IDers see their work as showing that ID is likely given IC. 

That is, IDers seem to represent their work as follows:

P(ID/IC) is high

OR

P(ID/IC) > P(ID/~IC)

Question: What do you think of Nagel's interpretation of ID?