"It needs milk," the poet said.
"I fed her," the mathematician said. (He had cleverly packed quite a lot of milk in his little bag, which he'd kept strapped tightly to his body even through the worst of the storm.)
"It needs to be cleaned," the poet said. Her tone had gotten a bit snippy.
"I changed her," the mathematician said. (He had also packed the necessary cloths for cleaning the child. Did I mention that he was clever?)
"It needs holding," the poet said, rising and starting to pace back and forth along the side of the road.
"You're doing that," the mathematician pointed out, "and I don't think you need to hold her quite so tightly."
"What does it need then? Why doesn't it stop crying?" the poet asked, her voice now almost as loud and frantic as the child's.
"Maybe she needs her mother to sing to her," the mathematician said.
"I can't! " The poet said. "I couldn't write the perfect song."
"Well, you'd better sing something," the mathematician said sharply. "You know I can't sing." They had agreed months ago that singing to the child would be her responsibility, and he was not about to let her back out of it now.