The goal, or purpose, of a thermostat is quite simple. It measures temperature and turns on/off an appliance or motor when the temperature is below or above a set point. The teleology of thermostats.

Heck, it's more complicated to explain than to use.

My house has a thermostat controlled by a 24 hour clock, with programmable high-low settings for active hours and for sleep hours. My housemate, B, showed me with a great sense of authority how it's done and that she had established the settings that we agree we prefer.

As if I didn't know how to program the thermostat in the house where it was installed nearly 20 years ago. (mumble, mumble)

But I nodded compliantly, because usually when she feels she's mistress of something then she will use it appropriately, though inconsistently.

Inconsistent, all right. Instead of just letting the furnace cycle on and off, she keeps moving the temperature markers around (mostly down to accommodate unseasonably warm weather), even at one point shutting the whole furnace off (thank god for electronic ignition!).

She just doesn't seem to "get" on a gut level, how a thermostat works, so I'll spend the morning freezing until I go downstairs to check and, sure enough, she's turned the furnace off again. For somebody who's smart and mechanically inclined, she sure is stupid about this.

Weird.