The latest progressive pet idea, which happens to be an old idea, is universal preschool. In his 2013 State of the Union address, President Obama proposed a plan whereby the federal government would partner with states to offer universal preschool, at a cost of $75 billion over 10 years.

The reason why progressives want to expand education is obvious enough: They like giving people free stuff.

Less flippantly, they think free universal preschool will make millions of families better off by removing a big burden on their time and finances, and they think it will make millions of children better off by giving them more education.

On the former point, they are certainly right that free universal preschool would make millions of families better off, although it would also punish those families that homeschool by making them pay for an entitlement they're not going to use.

On the latter point, the problem is that all the vaunted benefits of universal preschool have — how to say this politely — scant evidence in their favor. As David J. Armor and Sonia Sousa exhaustively detail in an article in the outstanding policy journal National Affairs, there's very little evidence that early childhood education helps boost test scores, let alone foster positive long-term outcomes. This is true even for the "high quality programs" that progressives say they favor when it is pointed out that Head Start's results aren't so great (thereby implicitly granting that Head Start isn't such a "high quality program"). This is true even when you apply the most sophisticated methodologies available to social scientists, randomized field trials.

The debate over early childhood education highlights a common theme in the left-right debate. The left proposes some ambitious new plan that's going to give everyone a unicorn. The right says, "Wait a minute, you're about to spend a gajillion dollars of other people's money, and unicorns don't even exist." And the left says, "Why do you hate widows and orphans?" At this point, the guy on the right starts to pour a stiff drink, only to realize that whisky has been outlawed (thankfully, ObamaCare covers medical marijuana).

Okay, this is a bit of a caricature. But just a bit.

In the progressive push for early childhood education, one is reminded of a Hail Mary pass. Perhaps the reason they want it so bad is because everything else has failed. As Ross Douthat pointed out in a very astute post, the modern welfare state has been very good at boosting people's incomes — and incompetent, or worse, at everything else it set out to accomplish, especially the sort of goals that progressives loudly insist early childhood education will do, like promote social mobility.

But the main reason the left pushes early education is actually very simple: Liberals think it will make the parents of millions of families better off. Even if free preschool doesn't turn everyone into Einstein, that's still a valid goal in itself.

This points to a deep failing of the right in public debate. While the left is prone to spend like a drunken sailor with too little regard for unintended consequences, the right has another vice. If the left proposes deeply flawed solutions to real problems, the right too often denies that these problems exist.

The climate change debate is paradigmatic in this case. Would a global regime of carbon taxation produce costs wildly in excess of any potential benefits? Absolutely yes. Is anthropogenic climate change still a real problem that we should do something about? Absolutely yes.

If conservatives are serious about policy and governing, then the onus is on them to offer real solutions to the pressing problems that the left is so quick to point out.

In this case, since the family is the bedrock of society, conservatives should make helping families with young children a big goal of public policy. Conservatives should put some meat on their pro-family rhetoric, not just point out the cost-benefit problems of universal preschool.

As Armor and Sousa point out, the government should first run a gamut of randomized field trials on early childhood interventions and preschool so we can have good evidence about what works and what doesn't.

More importantly, conservatives should introduce something that would give families more benefits than universal preschool: namely, choice. An expanded child tax credit, for example, could allow some families to choose preschool, and others to allow one parent step away from the workforce and take care of the children. Other families could choose a mix of approaches.

This would be a real conservative solution. More importantly, to see conservatives actually propose solutions to the actual problems of actual families, rather than offer bromides about "the family" and protests about left-wing overselling — well, that would be the real breakthrough.