Aidan's gift.

Aidan does not talk. He cannot stand, walk, or see. He will never do these things because his brain is atypical; in the womb it grew in a unique way - polymicrogyria (more and smaller cerebral folds), agenesis of the corpus callosum (absence of major tissue connecting the hemispheres) - and does not function like yours or mine. His mental capacities are severely limited. Perhaps his most complex accomplishment came when he was about two. He would call out in a lilting "ah," wait for our answer, also an "ah," and then respond in kind. We would go back and forth this way several times, he in his crib just across the hall from our room, all of us thrilled at mutual recognition. But he cannot do this now because a terrible seizure later stole even that ability from him.

Aidan hears quite well. When he is in a room full of six-year-old peers, his unseeing eyes sparkle and widen as he attends to the wonderful noise of chattering children. He takes in their sounds, pushes his feet against the jamb of his wheelchair, and smiles. Sometimes, though not as often as before the big seizure, he perks up at the sound of his mother, or his little sister, or me, his father, but especially his mother. She knows his strength, and bathes him in her voice, which he returns, on occasion, with a single contented coo.

For the most part, Aidan is serene. Reposed in his beanbag chair, a wordless Daoist presence, he does not remark or assess or condemn, but silently and sightlessly witnesses. There have been bad times: terrible weeks when kidney stones set him screaming, or desperate days of wheezing pneumonia. But he is usually peaceful and healthy, radiating a certain calm.

He is a physically beautiful child. His wavy brown hair flames a gentle, symmetrical face: almond-oval eyes with thick lashes evenly set over a lowbridged nose; round cheeks sloping down to neatly curlicued lips, neither too thin nor too thick; fair, smooth skin. Those eyes, though blind, are open and warm. He is free of the bodily contortions suffered by some people with severe physical disabilities. No spasticity to twist his limbs akimbo. No outward physical sign that there is any significant difference here. He is, quite literally, attractive. As a baby, people were drawn to him, invariably remarking on his good looks and grace. A handsome boy now, he invites attachment, friendship.

School is where he has made most of his friends. They greet him in the morning, sometimes bringing over their favorite stuffed animal for him to feel; they sit with him at story time or help him swirl his hands in finger paint. They make for him a world of sensations and relationships. He is now the eldest, a six-year-old in a class of fours and fives, but his silence and immobility mean that his age never manifests itself in more advanced vocabulary or physicality. The other children around him are never self-conscious of their youth; quite to the contrary, their abilities are magnified in the mirror of his limitations, and many of them comfortably congregate around him.

It is at school, too, that Aidan has the greatest effect on people around him. In his first year of preschool, one of his classmates had a noticeable speech impediment. Donnie's words were often unintelligible, drawing quizzical looks and sometimes giggles from his peers. As a result, he shied away from speaking, a reaction that could worsen his problem. The teachers and therapists did a good job engaging him and supporting his efforts, but he was very much aware of his idiosyncrasy and uncomfortable with it. In Aidan, however, he had an uncommon friend, one who did not strain to understand his words or laugh when they came out garbled. Aidan did not judge or correct. He just sat silently, varying little in his countenance whatever Donnie might say. On more than one occasion when I was in the classroom, I noticed Donnie close to Aidan, happily chatting away, gaining the practice he needed to clarify his speech. Aidan was able to help.

But as Aidan grows, school will pose a difficult question: What will the public get in return for its investment in his education? For the vast majority of disabled children, school provides the knowledge and skills necessary to be "productive members of society." That is the phrase most often used to justify special education and other remedial efforts. And it is a good thing. Not too long ago educatable children were warehoused in horrendous institutions, their potential stifled. Now many disabled young adults are living independently, earning some or all of their living and moving through society. It is a great victory. Aidan, though, will never live such a life. He will never have a job and pay taxes, never produce any wealth that might contribute to the costs of his health care, education, and other social services.

Yet the answer to the school question is easier than it might appear to an economist, insurance agent, or policy wonk. The payoff for Aidan's education is not measurable on a material scale. It is found precisely in his apparent lack of utility: He reminds us that humanity is beyond utilitarian calculus, that dignity cannot be captured in a cost/benefit analysis. And if anyone is looking to quantify the impact of Aidan's presence, just ask his friend Donnie. He'll tell you in clear, plain English.

Sam Crane is an associate professor of political science at Williams College, Williamstown, Massachusetts.