Efforts to understand human cognition are intimately tied to a focus on diverse languages. Research in the last several decades has offered evidence that linguistic diversity helps to foster differences in nonlinguistic cognition across populations. However, it has also been observed that linguistic diversity reflects common tendencies associated with a variety of types of thought. So careful inspection of linguistic diversity sometimes illuminates the depths of human cognitive diversity, but sometimes peels away a patina of cognitive diversity that covers underlying commonality of thought. In this paper I survey just a few of the findings that illustrate how linguistic diversity reflects both cognitive diversity and cognitive commonalities across populations. Numerical cognition receives particular attention, though several other aspects of cognition are touched upon as well. It is suggested that the diversity of "usage" of particular linguistic forms should play a greater role in the study of human cognition. The findings discussed are the cross-disciplinary product of varied methods. Taken together, they demonstrate that a more complete understanding of human cognition is dependent on the continued appreciation of, and emphasis upon, the multilinguistic nature of our species.