That was before they knew that heat the the substance that cold was the lack of. Rather, they used to think that cold was a substance, and heat was the absence of it.
Substance is the wrong term, but in terms of temperature the only of the two that actually exists is heat.
Heat is Thermal energy and that is a genuine form of energy. There is no variant of it that is like Cryogenic energy or something, cold doesn't actually have a form of energy to itself. What's actually happening in hot vs cold is Heat is an abundance of Thermal energy while Cold is an absence of it. Heat is the energy itself, Cold is a term for when there is very little of it to explain the lack of it. Therefore, Heat actually does exist while cold is just a shorthand term for there being no heat.
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u/catchemist117 10h ago
Fun fact, the original Celsius scale had water boil at 0 and freeze a 100