The languages of the world vary greatly, but within systematic limits that linguists have been uncovering for decades. Our research has been developing a unified explanation of semantic universals: properties of meaning shared by all natural languages. In this first talk, we will explain and defend our main hypothesis: such universals arise because expressions satisfying them are easier to learn than those that do not. We provide evidence for this hypothesis via computational experiments in three very different linguistic domains: quantifiers, responsive predicates, and color terms.