Have you ever thought to yourself, "How do I know that 2+2=4? Why isn't it 2+2+5?" PhD student @kareem_carr talks about numbers and abstraction with @PopMech https://t.co/UIo4MJsgqO @HarvardGSAS

— Harvard T.H. Chan School of Public Health (@HarvardChanSPH) August 30, 2020