Lemley on inducing patent infringement

Mark Lemley has an article Inducing Patent Infringement in 39 U.C. Davis L. Rev. 225
(Nov. 2005).

Lemley writes: Surprisingly, however, despite the venerable nature of inducement in patent law, the actual requirements for inducement liability have remained
something of a mystery. In particular, courts have proven unable to decide two
fundamental issues - what conduct might induce infringement, and what the inducer
must know and intend in order to be liable for acting.

Lemley points to three different possible definitions for inducement, each of which has some support in the caselaw:
(1) inducement is limited to causing infringement on a
respondeat superior theory;
(2) inducement extends beyond causing infringement to
include efforts to cause infringement, such as urging or encouraging
infringement by another; and
(3) inducement includes anything a defendant does to help a third party to infringe.

Lemley concludes: In my view, the right way to understand this seeming morass is not to choose either a single category of forbidden acts or a proper level of intent, but rather to recognize that these two variables should interact.

Lemley proposes a treatment analogous to the way inequitable conduct (materiality; intent) is handled: Thus, it seems to me that a sliding (or at least stepped) scale is appropriate, trading off greater involvement in the acts that
constitute direct infringement against a mental state of greater culpability. n82 The clearer the defendant's intent to facilitate patent infringement, the less direct his contribution need be. But the law correctly requires a threshold
showing on each element below which liability cannot be established. For conduct, that threshold is set by the active inducement requirement.