The phrase "voice of these children" seems to reveal the deeper thoughts and intuitions moving Justice Kennedy.

At today's oral argument in the Prop 8 same-sex marriage case.

Justice Kagan pushed the lawyer Charles J. Cooper to give some reason for excluding same-sex couples from marriage. Cooper seems to be trying to answer, saying that it's "reasonable" to think that "redefining marriage… as a genderless institution" could undermine marriage, making it less effective as a way to enforce "procreative responsibility." Seemingly unsatisfied, Justice Kennedy breaks in to say: "you should have to address Justice Kagan's question."

Cooper talks about how "it is impossible for anyone to foresee the future accurately enough to know exactly what [the] real-world consequences would be" if "this age-old bedrock social institution should be fundamentally redefined." This seems to be the interest in not changing anything until you have pretty good evidence that the change will be for the better. Justice Scalia tries to help, saying that if gay couples were married, there might also be a requirement to permit adoption. Even though California already permits same-sex couples to adopt, so how can California rely on the idea that it's bad for children. Scalia says that the requirement might apply to other states, and there is "no scientific answer" to the question whether having same-sex parents has a “deleterious effect" on children.

At this point, Justice Kennedy says this — boldface added:

I think... that there's substance to the point that sociological information is new. We have five years of information to weigh against 2,000 years of history or more. On the other hand, there is an immediate legal injury or legal -- what could be a legal injury, and that's the voice of these children. There are some 40,000 children in California, according to the Red Brief, that live with same-sex parents, and they want their parents to have full recognition and full status. The voice of those children is important in this case, don't you think?

The "Red Brief" is the respondents' brief under the Supreme Court's document preparation rules, but that's not the source of the "voice of the children" phrase. Searching the briefs, I found it in the amicus brief of the Family Equality Council:

The voices of children raised by same-sex parents — those who live every day within the family structure at the heart of these lawsuits — are too often unheard in the debates about same-sex couples and marriage. Their stories are too often missing from discussions of "traditional" families or "family values," and their personal experiences too often discounted as irrelevant. Although those who oppose marriage for same-sex couples frequently make assumptions about the quality of the children's family lives, the children themselves are rarely asked to explain what they actually experience.

This habitual omission is unfortunate because these children are uniquely qualified to speak about how their families look, feel, and function and how the availability — or unavailability — of marriage as an option for their parents colors their daily lives. These children are also among those persons most directly affected by both the Defense of Marriage Act (DOMA) and Proposition 8.

The voices of lesbian, gay, bisexual, and transgender (LGBT) youth are also too frequently disregarded in these debates. The laws banning marriage for same-sex couples or limiting federal recognition of such marriages leave these young people to question their own dignity and self-worth. This stigmatization has a profoundly negative impact on their self-esteem, sense of purpose, and well-being that threatens to burden them for the rest of their lives.

This brief presents the voices of these children.

If you want to know where Justice Kennedy's heart is. I think it's here.

Cooper stressed the lack of "data" about whether there's "any incremental beneficial effect” to the children in calling it marriage as opposed to just civil unions, but that's only saying there might not be a reason to include same-sex couples. Kagan's question was very specific: "So you have sort of a reason for not including same-sex couples. Is there any reason that you have for excluding them?" Kennedy demanded an answer to that question, and though he acknowledged the lack of information, he leaped from that to the injury to the voice of the children. Obviously, he meant there's an injury to the children and we need to listen to the voice of the children. There was something odd about that leap and the way it was phrased that makes it feel revelatory of the deeper thoughts and intuitions moving Justice Kennedy.