Most people think of the humanities as a group of disciplines, usually including some or all of the following: Philosophy, Religious Studies, Literature, Linguistics, History, Art, Art History, Music, Music History, Theater, Dance.
But defining the humanities in terms of a set of disciplines doesn't necessarily tell us much. What connects these things? Is there anything at all? We might think that they all have to do with "human activity", but of course, so does science and a whole lot of other stuff as well.
We could try to define the humanities in other ways. I have done so here, for an introductory graduate course I teach. But for our purposes, we are not trying to figure out how to do cutting edge research in the humanities at this point. We are, though, doing at least one thing in common with those graduate students - we are figuring out what a good question looks like.
In the end, that's what brings the humanities together - the kinds of questions it asks. In the sciences, we ask questions that lead to theories, or explanations of the world (e.g., why do wolves howl at the moon?). In practical disciplines like engineering, we ask problem-solving questions (e.g., how can we build a bridge over a river?). In the quantitative social sciences, we ask questions that help us understand how groups of humans respond to stimuli and influences, and also produce those stimuli and influences.
But in the humanities, we ask questions that are ultimately recursive, that is, that call ourselves into question. If we ask about why Hamlet acted the way he did, for instance, we are not only asking for a psychological account of his mental state, but we are asking about what it means to be human, and what Hamlet might teach us about that. When we look at a work of art produced in another culture or time, we ask not only how the artist produced it, but what it means, and furthermore, how it might help us understand a little bit better what it means to live in our world and experience it for ourselves.
In the end, the questions that we ask in the humanities are questions of meaning. And ultimately, the fundamental question about meaning is our own meaning. When we ask about that work of art from another time and place, we are really asking about the assumptions we bring to it that help us illuminate it, and also obscure parts of it. Experiencing the meaning that others have made always raises the question of our own meaning, if we are willing to pay attention.