An example of an historical alternative conception:
The following quotations from Kepler's essay on the shape of sowflakes suggest that (despite the referecne to reflecting on "whether cold is a force of nature like the Heat of the physicians. It had seemed a mere negation") he was thinking of cold as an active principle in it own right, not just an absence of heat:
"Finally, rounded shapes leave gaps, however closely they are bunched together, and thus cold would seek in through the gaps."
"When we had propose to inquire into the origin of this shape in snowflakes and to decide between external and internal causes the first to present itself was cold. Cold certainly gives rise to condensation, and by condensation vapour shrinks into the shape of a star, and so it seemed that cold gave it that shape. Then we went onto another reflection whether cold is a force of nature like the Heat of the physicians. It had seemed a mere negation, without a mind to design the hexagon and without any operations of its own….
Indeed, if cold is imagined as widely spread and vapour as meeting it on its outer surface only, it is more plausible that condensation should assume a quite flat shape, like the surface it meets, and that too of unlimited extent. For instance, if the whole outermost surface of the vapour were to acquire from cold density, from density weight, from weight downward motion, and from downward motion disintegration into crumbs of wafers, not all the wafers anyway, but rather very few, indeed I doubt if any at all, would turn out to be six-sided, still less with radii so symmetrically striped.""So let this issue be assumed as the ground of our submission, that, whatever the cause of these six rays may be, it is everywhere equally diffused in all directions. Hence if cold is the cause of the six rays, then cold surrounds each particle of vapour equally, or at least at equal intervals throughout. Alternatively, if internal heat is the cause, it too operates from one and the same centre in every dimension of a sphere."
"On this assumption, when the balls are so arranged, the cold will force its way through the gaps, but the balls will be protected against it from one point of contact to its opposite."
"This shows the superiority of the right-angled order over the oblique. But the cause which arranges the balls on this rather than that principe, is not yet in evidence. Surely cold cannot produce this effect? But how then is it produced?
For if cold produced any effect, it is that of condensation by penetrating the material either where there are gaps in it or where its resistance is feeble."
"I believe that the heat, which till then was protecting its matter, is now conquered by the surrounding cold…"
"…when cold engineers the break up of the uniform whole…"
"And gathered in is precisely what both matter and heat-engendering force are, under hostile attack from cold."
"If so, the cause of flatness would really be this: that cold touches warm vapour on a plane and does not surround all the vapour uniformly when starlets are produced as it does when it falls in lumps."
Johannes Kepler
Kepler, J. (1966). A New Year's Gift. Or, on the six-cornered snowflake (C. Hardie, Trans.). Oxford University Press. (Original Latin edition, 1611)
