Composition is the conclusion that just because an element of something has a certain property, that the larger thing must also have that same property. Composition is the converse of Division.
Pretend it’s 2005 for a moment, you’re at home with a bunch of friends, you’re all in front of the TV with your popcorn and your soda and you’re watching the ABC series Lost. Still shaken from the terrifying revelation that Ethan was not on the plane, when suddenly John Locke and Boone uncover the hatch! In this moment of passion, if one were to proclaim that Lost will quite clearly be one of the best TV shows ever written, they would have fallen for Composition. It would have been better to concluded that this episode is the best, and in no way is that a predictor for the gnarled mess to come. Okay, so this isn’t the best example. Quality is subjective yada, yada, and for someone out there, Lost is the best show ever written, but we all know that they are wrong. Breaking Bad.
Oxygen is a gas*, and hydrogen is a gas*, therefore H2O is a gas*.
Swallowing a piece of gum is harmless, therefore swallowing a box of gum is harmless.
If I let my dog poop on the sidewalk, my life will be easier. Therefore, if everyone lets their dog poop on the sidewalk, everyone’s life will be easier.
*When outside at room temperature/sea level/on earth. (All three elements listed can be either gas or liquid depending on their temperature and the pressure they are under. Thanks James for spotting this!) https://en.wikipedia.org/wiki/Phase_transition