Examples of historical scientific ideas that would now be considered alternative conceptions:
"It was necessary in the first place that they should be able to identify the chemical elements, but the simplest examples were perhaps the most difficult of all. For thousands of years, air, water and fire had been wrapped up in a myth somewhat similar to the myth of the special ethereal substance out of which the heavenly bodies and celestial spheres were thought to have been made. Of all the things in the world, air and water seemed most certain to be irreducible elements, if indeed – as Van Helmont suggested – everything in the world could not be resolved into water. Even fire seemed to be another element – hidden in many substances, but released during combustion, and visibly making its escape in the form of flame. Bacon and some of his successors in the seventeenth century had conjectured that heat might be a form of motion in microscopic particles of matter. Mixed up with such conjectures, however, we find the view that it was itself a material substance; and this latter view was to prevail in the eighteenth century."
Herbert Butterfield (1957) The Origins of Modern Science 1300-1800 (New Edition: Revised and enlarged). G. Bell and Sons Ltd., London.
