Refers to two UK patent cases, Catnic Components Ltd and Another v Hill and Smith Ltd, [1982] RPC 183 and Improver Corp v Remington Consumer Product Ltd, [1990] F.S.R. 181) in which the principle of ‘purposive’ patent claim construction, i.e., patent claims must be interpreted purposely through the eyes of the person skilled in the art to whom the patent is addressed, was set out. ‘Purposive’ is in essence a recognition that language is an imperfect medium for communicating technical concepts, particularly the new concepts that, in principle, might be described in a patent, and that therefore allowance should made for inherent difficulties in, or unforeseen implications of, drafting which have resulted in the literal construction not being the one the drafter has obviously intended; i.e., consider the ‘purpose’ of the language and not its literal meaning. Arguably, Catnic/Improver imported the doctrine of equivalents into English Patent Law.