Logic 8 - A datum can be evaluated only by a datum of comparable magnitude.
Once you think up some examples this logic is "obvious" but like so many things it isn't actually "obvious" until you understand it.
Your friend has just been on a mountaineering trip. "So Joe, how big was that mountain you just climbed?" Which answer makes sense?
- Answer 1: "Well, see this grain of sand? The mountain was much much bigger."
- Answer 2: "Almost as high as the Matterhorn"
Answer 2 makes the most sense because the Matterhorn and Joe's mountain are of comparable magnitude, whereas a grain of sand and Joe's mountain are not of comparable magnitude.
A less obvious example would be this: Bill is extremely sick and has a temperature of 102F. The doctor tells him to take an aspirin. This makes no sense because an aspirin is an answer to something with the order of magnitude of a headache not a raging fever.