Both. Students are required to take humanities classes as well as declare a concentration. Many often choose to minor or major in humanities alongside a science or engineering degree. A handful end up graduating with only a humanities degree. My high school physics professor actually graduated MIT with a writing degree before returning for a PhD in physics.

I myself double majored in Music Composition and Computer Science and have spent my career so far working at their intersection. The strength of their music department was a big part of the reason I applied to and attended MIT.