The Alchemist's Daughter

I'm reading an interesting novel right now called The Alchemist's Daughter by Katherine McMahon. It's a historical fiction about a girl growing up in the early 1700's who follows her father's footsteps and teachings into the world of "Natural Philosophy" - what we would today call Biology. As a scientist, it's an interesting read for me because there is so much scientific knowledge that I take for granted. Daily calculations of molar concentrations, molecular weights and percentage solutions come so naturally to me that it is difficult to imagine a time before the theory of the atom. One of the large scientific debates in the novel is over the nature of fire - which was considered a primary element along with water, air and earth - and the prevailing thought is the idea of phlogistation. Fire was thought to release a material called phlogiston and an item would only be flammable until it took in as much phlogiston as it could hold. Hence when a candle is burned in an enclosed space, it will go out when the air has become saturated with phlogiston. Of course such notions seem ridiculous today - and part of me wants to scream about elemental oxygen to the characters - but there is certainly merit in the creativity of the thinkers of that age.

Oftentimes it's obvious to look at inventions - the printing press, lightbulb, steam engine, cotton gin, telephone or radio - that have changed the course of history and daily life as we know it. However, it is much less often that we think about the ideas that have impacted the world in massive ways. Revolutionary inventors are usually listed as Whitney, Edison, Bell, etc. where as Galileo, Newton, and Rutherford were geniuses as much and more. The ice breaker is often raised "What's the greatest invention before sliced bread?" but I'd like to open the discussion "What's the greatest IDEA before slicing bread?"

Think creatively and defend your answer.