it's not a paradox.

it's a reductio ad absrudum, demonstrating the fundamental wierdness of the copenhagen interpretation of quantum mechanics.

(i'm too tired to look things up right now, so i'll just say it as best as i can remember it)

one of the things in quantum mechanics is the idea that at SOME size/energy scale, things stop acting quantum-y and start acting classical-y. mostly, i think people wave their hands and hope that some day someone will come up with a really good explanation of where that size scale is, and why it is. I bet the quantum computer people have a good explanation by now.

anyway, Schrodinger was demonstrating that you can imagine a situation where the quantum mechanical nature of an object (the radioactive isotope) can dictate to the macroscopic world (the cat). while the box is still closed, you might as well treat situation in the box in terms of the quantum states of the isotope which dicate it's state. so the cat has two quantum states: alive and dead, and before the box is opened, It's "un-measured state" is a linear combination of the two.

so the cat is both alive and dead, just the way the radioactive isotope is both decayed and not decayed.

which is stupid. the cat has to be one. or the other. right?

so maybe those jerks in copenhagen are wrong.

or maybe the cat is quantum.

the moral of the story isn't that there is some lesson to learn about cats: rather it's that we shouldn't treat the philosophical picture underlying the copenhagen interpretation as being irrelevant to the macroscopic world.