In the "history of science" group I posted a remark on the apparent parallelism between the "four classical elements" air, water, earth, and fire and the three phases of matter apparent to unaided observation plus "energy" (fire). We wondered whether these were "fundamental" or not, and I remarked on the pair of oppositions "wet/dry" and "hot/cold" which supposedly underlay the "elements" - the precise sequence being (according to Wikipedia - http://en.wikipedia.org/wiki/Classical_Elements) :
AIR is primarily wet and secondarily hot.
FIRE is primarily hot and secondarily dry.
EARTH is primarily dry and secondarily cold.
WATER is primarily cold and secondarily wet.
If you'd look at the Wikipedia articel, I'd draw you attention to the diagrammatic representation of the “diamond” of the elements and the “square” of the oppositions. The ‘primary’ characteristic of each element is given by the quality positioned anticlockwise to the element; the secondary characteristic by the quality positioned anticlockwise.
This explains why Water should be, surprisingly PRIMARILY cold and Air should be PRIMARILY wet. Any other sequence leads either to elements being, for example, “wet and dry” or to the definition of water as “primarily wet and secondarily hot”, which is contrary to our general experience of water in nature.
So, the apparent states of things (solid, liquid, gas, “energy”) and the apparent characteristics of those states (being wet or dry; being hot or cold) are drawn from phenomenal experience; but as soon as that experience is regimented into some kind of “protomodel”, it leads to counterintuitive results.
The problem lies in the characteristics chosen. Fire evidently has the characteristic of being cold; water evidently has the characteristic of being wet. A large number of solids have the property of being dry, thus completing the opposition “wet/dry”; given that fire is *evidently* both hot and dry, this allows only the combinations “dry and cold” OR “wet and cold” OR “wet and hot” to describe the other elements.
Water is evidently not dry, so it must be either “wet and cold” or “wet and hot”. Furthermore, neither “wet and cold” nor “wet and dry” are sufficient characterisations of the phenomenal qualities of earth; therefore, it can only be cold and dry. We’re left with the choice between “wet and cold” and “wet and hot” for either Water or Air.
There is no particular reason for the choice of one or another save observation of the interactions of fire and water and of fire and air. In sufficient quantities, water douses fire, while blowing air onto a fire usually enlivens it (though it can extinguish it). Therefore, Air and Fire must “share” a characteristic; given that by elimination we have assigned the characteristic “dry” to Earth, this characteristic must be “hot”. Air communicates its heat to fire, though in the wrong proportions, the “wetness” of Air can lead to the extinction of the fire; Water is always either sublimated by a fire into Air (the “cold” becomes “hot”) or itself converts the fire into Earth, or ash (the “heat” becomes “cold”).
What’s interesting is that, even in a model based directly on our phenomenal experience and on our immediate intuitions about that experience, there’s a degree of counterintuitivity introduced by the “formal requirements” of the model; furthermore, these counterintuitive results are then “explained” by appeal to the “predicitive success” of the model... you can imagine the discourse:
“Well, yes, I know that it seems odd to say that Water is only secondarily wet, and I know that Air doesn’t usually seem particularly wet OR hot; but these characteristics explain why Water extinguishes Fire or is completely dispelled by it and also why Air can enliven Fire, so it MUST be right...”
And we talk as if “counterintuitive physics” were something new...
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