Insanity comes in two basic varieties: slow and fast.

I'm not talking about onset or duration. I mean the quality of the insanity, the day-to-day business of being nuts.

There are lots of names: depression, catatonia, mania, anxiety, agitation. They don't tell you much. .

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Take a thought -- anything, it doesn't matter. I'm tired of sitting here in front of the nursing station: a perfectly reasonable thoughts. Here's what velocity does to it.

First, break down the sentence: I'm tired -- well, are you really tired, exactly? Is that like sleepy? You have to check all your body parts for sleepiness, and while you're doing that, there's a bombardment of images of sleepiness, along these lines: head falling onto pillow, head hitting pillow, Wynken, Blynken, and Nod, Little Nemo rubbing sleep from his eyes, a sea monster. Uh-oh, a sea monster. If you're lucky, you can avoid the sea monster and stick with sleepiness. Back to the pillow, memories of having mumps at age five, sensation of swollen cheeks on pillows and pain on salivation -- stop. Go back to sleepiness.

But the salivation motion is too alluring, and now there's an excursion into the mouth. You've been here before and it's bad. It's the tongue: Once you think of the tongue it becomes an intrusion. Why is the tongue so large? Why is it scratchy on the sides? Is that a vitamin deficiency? Could you remove the tongue? Wouldn't your mouth be less bothersome without it? There'd be more room in there. There tongue, now, every cell of the tongue, is enormous. It's a vast foreign object in your mouth.

Trying to diminish the size of your tongue, you focus your attention on its components: tip, smooth, back, bumpy, sides, scratchy, as noted earlier (vitamin deficiency), roots -- trouble. There are roots to the tongue. You've seen them, and if you put your finger in your mouth you can feel them, but you can't feel them with the tongue. It's a paradox.

Paradox. The tortoise and the hare. Achilles and the what? The tortoise? The tendon? The tongue?

Back to the tongue. While you weren't thinking of it, it got a little smaller. But thinking of it makes it big again. Why is it scratchy on the sides? Is that a vitamin deficiency? You've thought these thoughts already, but now these thoughts have been stuck onto your tongue. They adhere to the existence of your tongue.

All of that took less than a minute, and there's still the rest of the sentence to figure out. And all you wanted, really, was to decide whether or not to stand up.