The island of Key Biscayne, Fla., sits in the Atlantic Ocean 10 miles southeast of Miami. Its 10,000 residents depend on the Rickenbacker Causeway, a four-mile-long toll bridge connecting the island to the mainland, for all their supplies. Right now all vehicles passing through must pay a set toll—$1.50 for cars, $9.00 for three-axle cargo trucks, and so on. But what would happen if a bridge owner decided to charge a toll based not on the size of a vehicle but on the cargo it was carrying? He could let his brother’s lumber-supply company through for free and make its chief competitor pay through the nose. He could force the Winn-Dixie grocery store to double its prices, pushing area residents to local restaurants. In short, the bridge owner would have the power to control everything that the residents of Key Biscayne have access to.

This is the essence of the widely discussed but little understood concept of “net neutrality.” The bridge, in this case, represents the lines that carry the Internet to your home computer or smart phone. So far Internet service providers have for the most part treated all content equally. The worry is that, sensing a business opportunity, they might strike deals with certain content providers to deliver faster access for a fee or to block some information entirely. The worry isn’t completely theoretical; Comcast recently told the company that delivers Netflix streaming videos that it needed to pay up if it wanted to access Comcast’s customers. (Lost on no one was the fact that Netflix directly competes with Comcast’s own video-on-demand service.)

To make matters worse, most Americans have only one choice of high-speed broadband provider; the most fortunate have two. Unhappy subscribers cannot just leave and get their Internet elsewhere. This effective monopoly leaves consumers with little protection from a provider that has the means to filter everything that they can buy, watch and read.

Internet service providers contend that they must retain the flexibility to manage their networks in the way they see fit—slowing or blocking some high-bandwidth applications to ensure reliable service for all. Network management is a serious concern, but it must not become a cover for policies that censor any content displeasing to the corporate gatekeeper. The Federal Communications Commission approved a rule last December that was intended to ensure equal treatment of content providers. Yet while the FCC rule prohibits “unreasonable” discrimination of network traffic, it fails to spell out what unreasonable behavior entails. The ruling is vague in ways that only a Washington, D.C., lawyer could love; the only certainty it gives is of the tens of thousands of billable hours to be spent arguing over the meaning of “unreasonable” in federal court.

The fix, however, is simple. As the FCC goes about enforcing this ban on so-called unreasonable policies, it should clarify that the only kind of unreasonable discrimination is discrimination against particular applications.

What would this mean in practice? Instead of the “all you can eat” data plans of today, Internet service providers could sell customers access by the gigabyte. They could limit performance at peak times of the day to help balance network load or offer superfast plans at higher prices.

Internet service providers would not, however, be able to determine which applications go fast and which go slow. They would not be able to reach a deal with Facebook to speed up that site’s page loads while slowing down LinkedIn. They could not put Skype calls through a bottleneck or throttle back all video-streaming sites, because these are all judgments based on application. This clarification gives Internet service providers the leeway they need to maintain healthy networks, as well as plenty of incentive to invest in advanced network infrastructure for those customers willing to pay for ultrahigh-speed service. But it takes away the power of Internet service providers to choose winners and losers. We can accept that a bridge owner can charge vehicles based on their size—$1.50 for cars, $9.00 for three-axle cargo trucks—but a democratic society can’t abide discrimination based on content.