Arguments from similarity

I thought some more about the evolution argument I discussed yesterday, and decided that, the argument is sufficiently general to be addressed by general logical principles, and does not require detailed knowledge of the science of DNA. The argument is that Unqualified appeals to similarity do not demonstrate common descent any more than they demonstrate common design. Which is absolutely correct. The argument “X’s are similar, therefore X’s have a common descent” lacks a middle, and is therefore invalid. To make it valid, we need a premiss that connects the term ‘similar’ to the term ‘have a common descent’. The premiss ‘X’s that are similar have a common descent’ would clearly do, but is clearly untrue. For example, pebbles that have been washed over by the tide for many years are all similar in that they are smooth, but they have no common descent. Snowflakes all display a common form, but have no common descent, etc.

The real principle we need to appeal to is that things which are similar are (or are highly likely to be) similar by a common nature or cause. The scholastics had a wonderful word for this: ratio, which has a common meaning that cannot be translated by any single word, but which in the present context would be translated by ‘reason’ or even ‘explanation’. When we see things with an identical or similar structure, there should be a explanation or reason for this. Pebbles washed by the tide are smooth for the very reason that they are washed by the tide, being knocked against other pebbles, smoothing the pointy bits. Snowflakes are similar because they are all water, which has a consistent molecular structure (at least I assume so, otherwise I’ll leave this to experts).

Primates and humans share similar DNA. There should be a reason for this. One reason is that God made the DNA similar. But is there a simpler explanation? Surely there is. Science tells us that DNA is a highly complex molecule. Common experience tells us that DNA is very ‘weak’ – it degrades quickly outside its natural environment, which is a living organism. So DNA cannot randomly occur. We also know, from common experience, that it can occur by reproduction. Humans reproduce other humans, primates reproduce primates, plants reproduce plants. (I have a spider plant in the attic that I have replicated for more than 20 years by the usual well-understood techniques). So, one simple explanation for the similarity of DNA is that it replicates itself. It reproduces its form in matter (Carbon, Hydrogen, Oxygen etc. molecules).

Thus, the simplest explanation of the similarity of form of DNA is by replication or reproduction. This does not require invoking a designer who caused the similarity.

Evidence for evolution?

An interesting article here.  Interesting because, though apparently by a Christian fundamentalist anti-evolutionist, who in my experience are not the most cogent or reasonable of apologists, it does indeed appear cogently and reasonably written.  For example, he says "Unqualified appeals to similarity do not demonstrate common descent any more than they demonstrate common design".

Since I know practically nothing about evolution, and rarely watch nature programs mainly because I dislike animals (smelly, poor conversationalists), I leave it to others to comment.

Stephen Law versus William Lane Craig

I’m thinking of going to the debate between ‘Christian Apologist’ William Lane Craig, and atheist philosopher Stephen Law:

17th October 2011 from 7:30pm – 10pm
Westminster Central Hall, Storeys Gate, London, SW1H 9NH
Premier Christian Radio Debate on the existence of God against atheist philosopher Stephen Law, who is also editor of the magazine of the Royal Institute of Philosophy THINK.

Law discusses it on his blog in several posts, the latest of which is here. One of the commenters on Stephen’s blog says

This is not being regarded as a game or some dry academic exercise by them. You are there to be beaten, defeated, humiliated and ridiculed, and, by extension, so is the whole atheistic worldview that you represent.

But then again, perhaps not. In what sense one can ‘win’ a debate like this? A show of hands is foolish, given who will be turning up (diehard supporters of Law, diehard supporters of Craig, neither side likely to be convinced by any argument on the opposing side). The only way to ‘win’ at logic is to survive careful analysis of your arguments, performed in a dark and quiet room, for at least five hours, alone. Logic and debate are quite different things, as is obvious from the following comments at an atheist website 

William Lane Craig is a prolific Christian philosopher, apologist, author, and public debater. He is the best debater – on any topic – that I’ve ever heard. As far as I can tell, he has won nearly all his debates with atheists. When debating him, atheists have consistently failed to put forward solid arguments, and consistently failed to point out the flaws in Craig’s arguments.

I.e. it is conceded that Craig is a good debater, yet his arguments are flawed.

Also, I was really not sure who to support. I studied Craig as part of my theology diploma, and I thought his arguments were slippery and crowdpleasing. On the other hand, I have a visceral dislike of atheism. In the end, Michael Sullivan decided it for me. In an excellent post here, he says that “One does not reason to Christianity or reason to Catholicism in the sense that philosophy ever proves (in any sense) that the Christian doctrines are true.”

That is entirely Ockham’s position (as I understand it). So I shall support Law against Craig, as if it mattered. Is Michael right? Well, Thomas thought you could reason to Christianity, and perhaps prove it in some sense. And Phillips has this to say:

Just as in S. Thomas's day there were those who maintained that the existence of God is to be accepted by faith alone, and so is not to be demonstrated, so there are also in our own. It is, in fact, felt by those who take this view to be, in some sort, impious to attempt to prove what they firmly believe; and possibly there is mixed with this attitude a kind of false mysticism, as if they had already a kind of direct intuition of God. All that has been said earlier as to the nature of the human intellect and its proper object runs counter to such an idea as this, for we are convinced that we know the immaterial and supersensible by means of the material and sensible; the proper object of man's intellect being the natures of material things. Moreover, it is clear that to say that we know God's existence by faith is to make an assertion which refutes itself, since no one can accept anything on the authority of God, i.e. by faith, who is not first convinced that there is a God. Hence S. Thomas says here in answer to this objection, that the existence of God is not an article of faith, but one of the 'preambula' to the articles of faith, natural knowledge being presupposed by faith, as nature is by grace, and in general that which is perfectible by perfection. (my emphasis)

The argument from beauty

I just discovered the ‘argument from beauty’. There is a brief description in Wikipedia, and a more detailed one here. The argument may be summarised as follows:

Beauty exists in a way that transcends its material manifestations
According to materialism, nothing exists in a way that transcends its material manifestations
Therefore, materialism is false

I wonder if there is a fallacy here similar to the one about trees being made high enough so that giraffes did not have to lean down, or the sun moving the way it does in order for crops to be harvested at the right time.

Perhaps objects are beautiful in the way that food tastes good. It would be obviously fallacious to argue that God made food taste that way in order that we would enjoy it, would want to eat it, and so would not starve. Clearly, our nervous system has adapted that way. Are there similar reasons for things looking beautiful to us?

Adamson on Anaxgoras

I just listened again to Peter Adamson's podcast about Anaxagoras.  Entertaining and improving, and an interesting characterisation of the argument from design.

There is a grand tradition, in both philosophy and religion, of invoking God, or the gods, to explain the fact that the world looks so well designed. Think about how the sun moves in just the right way to give us the seasons, so that we can plant and harvest food to keep ourselves alive.  Think of the giraffe with its long neck - just the thing for reaching those tasty leaves in the trees.  Think even of how much it hurts when you step on something sharp. Sure, you don't feel grateful when it happens, but if not for the pain, you would be a lot less careful in the future, and you would probably wind up with cuts all over your feet and then where would you be? So, even the bad things in life seem designed to make things better. Socrates assumed that is was roughly where Anaxagoras was heading when he put mind in charge of the cosmos.

The argument about the sun moving in just the right way is not exactly parallel to the argument about giraffes.  For them to be parallel, it would have to be argued that God created trees at just the right height so that giraffes, with their long necks, would not have to be constantly be leaning over and getting backache, or toppling over.

There is more to be said about arguments from design generally.  What are they?  What do they argue from?  What are they arguing for?

Anaxagoras and the argument from design

Anaxogoras (500-428 BC) seems to have been the first to suggest that ‘blind’ causation and deterministic mechanical features of the world cannot explain the order and harmony we see in the universe. Many or all of the operations of nature seem to be directed towards specific ends. Anaxogoras – apparently reacting to contemporary atomistic theories that deterministically explained everything in terms of fixed laws of the motion of elementary particles – thought that such design was evidence of an agency which was rational and non-physical. This idea clearly appealed to Aristotle, and may have been an influence on his thought. He speaks approvingly:

When one man said, then, that reason was present - as in animals, so throughout
nature - as the cause of order and of all arrangement, he seemed like a sober
man in contrast with the random talk of his predecessors. We know that
Anaxagoras certainly adopted these views, but Hermotimus of Clazomenae is
credited with expressing them earlier. Those who thought thus stated that there
is a principle of things which is at the same time the cause of beauty, and that
sort of cause from which things acquire movement. [Metaphysics book I, 984b18

Without doubt, the idea became influential as a result of Aristotle. He argues (in Book 12 of the Metaphysics) that the world is moved by an eternal prime mover who is the source of all process and change, while not itself subject to process or change. This substance does what is the highest form of life ought to do, namely to think. ‘The rule of many is not good; one ruler let there be.’ Thomas Aquinas finally unified Catholic and ancient Greek with this idea at its centre.

Sed pluralitas principatuum non est bonum. Sicut non esset bonum quod essent
diversae familiae in una domo, quae invicem non communicarent. Unde relinquitur
quod totum universum est sicut unus principatus et unum regnum. Et ita oportet
quod ordinetur ab uno gubernatore. Et hoc est quod concludit, quod est unus
princeps totius universi, scilicet primum movens, et primum intelligibile, et
primum bonum, quod supra dixit Deum, qui est benedictus in saecula saeculorum.
Amen. [Commentary on the Metaphysics, book 12]

*Note (quick advertisement for the Logic Museum) that the Museum is still, AFAIK, the only place on the internet where you can link to Aristotle via Bekker numbers. The coverage and scope of Aristotle, and the medieval writers who cited his work, is increasing all the time.