Humans are remarkable creatures. This one species has explored its own world and ventured into space. We've shown compassion toward one another in times of need. We've waged wars that spanned the globe, killing millions of our own kind for various reasons. And we've used the gray matter stored in our skulls to observe the world around us and determine how stuff works. 

Making a list of amazing intellectual achievements is both easy and difficult. It's easy because humans have been around for a long time and we've achieved many things. It's difficult because the list of candidates is enormous -- how do you determine which ones make it in?

This list isn't ranked in any particular order. It's not an exhaustive account of the best of the best. Rather, it's a selection of achievements that have shaped how we perceive and understand the world.