Patents are, in theory, a legal right to exclude competitors from using the patentee's invention. Exactly what the patentee gets to prevent others from using depends, however, on how the law defines the scope of the patent right. In modern American patent doctrine, we define what the patentee owns not by what she actually built or disclosed, but by what she claimed. Courts and commentators regularly analogize patent claims as akin to the "metes and bounds" of a real property deed, defining the outer boundaries of a "property" right conferred on the patentee. According to this view, known as the peripheral claiming approach, words of a claim form a sort of conceptual "fence" that marks the edge of the patentee's rights. And for the last dozen years, judges have had the responsibility of defining that periphery, interpreting the perimeter of patent claims in a pretrial proceeding known as a Markman hearing.

It isn't working. Despite repeated efforts to set out the rules for construing patent claims, culminating in the Federal Circuit's en banc Phillips decision in 2005, parties and courts seem unable to agree on what particular patent claims mean. Patent law has provided none of the certainty associated with the definition of boundaries in real property law. Literally every case involves a fight over the meaning of multiple terms, and not just the complex technical ones. Recent Federal Circuit cases have had to decide plausible disagreements over the meanings of the words "a," "or," and "through," to name but a few. Claim construction is sufficiently uncertain that many parties don't settle a case until after the court has construed the claims, because there is no baseline for agreement on what the patent might possibly cover. Even after claim construction, the meaning of the claims remains uncertain, not only because of the very real prospect of reversal on appeal but also because lawyers immediately begin fighting about the meaning of the words used to construe the words of the claims.