"Water produces cold" is a plausible hypothesis for someone using Earth/Air/Water/Fire chemistry.
They did well enough to figure out or intuit or guess that a simpler explanation was better: You're not giving them enough credit, as some went beyond that chemistry.
All things are an interchange for fire, and fire for all things, just like goods for gold and gold for goods.
Aristotle speaking about Thales:
"For it is necessary that there be some nature (φύσις), either one or more than one, from which become the other things of the object being saved... Thales the founder of this type of philosophy says that it is water."
See also...
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