Note that the Free Will Theorem directly contradicts the article’s claim that knowing the exact state of the universe allows you to compute the future.

Update (2/21/10): Trackpads with separate buttons now feel really strange. And I love how far back the display tilts — much further than any other laptop I’ve ever used, and so much more comfortable!

Side effects are eliminated by avoiding (1) global variables and (2) functions that modify their arguments.

Point #1 is relatively easy in any language (except assembly), but it does require discipline, since global resources like files and databases are in principle always directly accessible, even if an encapsulating interface exists.

Point #2 is very difficult/painful in strongly typed languages like C++ and Java but very easy in untyped languages like Lisp, Perl, and JavaScript, mainly because untyped languages make it very easy to return a heterogeneous list of values/objects.

This is what has been bothering me about Lisp in the back of my mind: a list is the most natural return value, both because the syntax is simple and because most standard functions operate on lists. A homogeneous list is fine, of course, but a list of heterogenous values is terrible because (1) it is hard to remember what is returned in each slot and (2) without compile time checks, modifying a function to insert a new value into the returned list creates a maintenance nightmare. You have to manually find and update every use of the modified function, and if you miss one, you have a subtle bug.

How can we avoid all this trouble? Using a map instead of a list alleviates the problems because (1) well chosen key names are easier to remember and (2) most of the existing uses of the function probably will not need to be updated because they do not care about the new value and the original values will still be accessible via the same keys.

Unfortunately, working with maps (or hash tables) in Lisp is a lot messier than working with lists. In Perl and JavaScript maps are part of the language syntax.

I was very skeptical when I read that James Cameron was out to out-Lucas George Lucas. I don’t believe it’s possible, but only because every game changing quantum leap up has the same general effect of blowing the public’s collective mind. But there is no question that Avatar has now changed the game in exactly the same way that Star Wars did thirty years ago. Audiences will not put up with 2D summer blockbusters much longer.

The story is certainly not as sweeping in scope as Star Wars, but Cameron deserves credit for at least thinking up an entire continent instead of only a few square miles of jungle. The characters were all stereotypes, and they died in the standard order, but they were still well done and served the purpose of making as deep an emotional impact as possible. As far as I can tell, that was what Cameron wanted: amplify the impact of watching full 3D by giving the audience characters to whom they can readily respond.

When I went to find the book on Amazon, I discovered that there is a whole cottage industry based on writing books like this. I was a bit surprised, but I really shouldn’t be. People on both sides of the debate never cease to propound their opposing views. Why shouldn’t there be a group who tries to bridge the chasm?

The sad part is that all three groups mostly get it wrong. Regardless of the point of view — be it bible only, bible+science, or science only — they almost always fall into the trap of thinking that they actually know how the universe really works.

The fact is, we don’t.

We cannot prove that God exists. If He does not exist, we are left wondering how the universe came to exist and what our purpose is, if any. If He does exist, we are left wondering how He came to exist and, if you accept the Bible, why He behaves the way He does.

It is quite humbling to admit that we just don’t know what is really going on. It is also scary, however, which is probably why most people cling desperately to one viewpoint or another. (This applies to all religions, not just Christianity.)

However, if people would accept this dose of humility, then I think we would all find it much easier to get along.

Since we want her bed to be against the wall, away from the window, one of the two under-the-bed drawer sets wouldn’t make any sense under the bed, so we put it in the closet. It fits so perfectly that I’m tempted to start believing in Intelligent Design