For Thomas Aquinas, the human is a paradox. As "rational animals", we are the only species that straddles the divide between matter and spirit. We do not just inhabit the material world – we interpret it, discern order within it, derive meaning from it and act decisively upon it. Our intellects transcend their material confines with a unique freedom and imagination.
Today, this is referred to as the problem of consciousness. How did a species jump the evolutionary tracks and acquire a capacity to reflect upon its existence within a world of which it is a part and to whose laws it is subject? Questions like this are fundamental to our understanding of what it means to be human.