"514 The classic case of direct evidence of unlawful purpose occurs when one induces commission of infringement by another, or “entic[es] or persuad[es] another” to infringe, Black’s Law Dictionary 790 (8th ed.2004), as by advertising. Thus at common law a copyright or patent defendant who “not only expected but invoked [infringing use] by advertisemen t” was liable for infringement “on principles recognized in every part of the law.” Kalem Co. v. Harper Brothers, 222 U.S., at 62-63 (copyright infringement). The rule on inducement of infringement as developed in the early cases is no different today. Evi dence of “active steps … taken to encourage direct infringement,” Oak Industries, Inc. v. Zenith Electronics Corp., 697 F.Supp. 988, 992 (N.D.Ill.1988), such as advertising an infringing use or instructing how to engage in an infringing use, show an affirmative intent that the product be used to infringe, and a showing that infringement was encouraged overcomes the law’s reluctance to find liability when a defendant merely sells a commercial product suitable for some lawful use. For the same reasons that Sony took the staple-article doctrine of patent law as a model for its copyright safe- harbor rule, the inducement rule, too, is a sensible one for copyright. We adopt it here, holding that one who distributes a device with the object of promoting its use to infringe copyright, as shown by clear expression or other affirmative steps taken to foster infringement, is liable for the resulting acts of infringement by third parties. We are, of course, mindful of the need to keep from trenching on regular commerce or discouraging the development of technologies with lawful and unlawful potential. Accordingly, just as Sony did not find intentional inducement despite the knowledge of the VCR manufacturer that its device could be used to infringe, mere knowledge of infringing potential or of actual infringing uses would not be enough here to subject a distributor to"