the circuits. Free World Trust sued Électro Santé for patent infringement on the ground that although the means may be different the end result of the inventions were the same. The Quebec Superior Court found that Électro Santé's invention was not novel and so their invention was invalidated. The Court of Appeal overturned the decision and found that there was no violation. In a unanimous decision, the Supreme Court upheld the appellate court ruling. Opinion of the court Justice Binnie wrote the decision for a unanimous Court. He began by describing the process of interpreting a patent through "claim construction". Claim construction is the process where the inessential part of the patent are distinguished from its essential elements which are protectable by patent. In this case, the essential elements of the two patents held by Free World included controls that regulated the electro-magnetic waves "by circuit means". This invention, Binnie found, was more than a mere aggregation of known components and was not anticipated by publications. The primary issue to Binnie was how to resolve the conflict between "literal" and "substantive" infringement. He states that one of the purposes of the Patent Act is to achieve fairness and predictability in order to promote research and development. He was concerned that protection provided by a broad reading of a patent would scare innovators from exploring similar ideas surrounding a claimed patent. According to Binnie, predictability could be achieved by "tying the patentee to its claims" and fairness would be achieved by "interpreting those claims in an informed and purposive way". Binnie was hesitant for courts to attempt to find the "spirit of the invention" which would create more uncertainty and unpredictability. His proposed "purposive construction" approach would avoid literal interpretation while limiting the scope of substantive claims in attempt to balance fairness between the patentee and the public. Purposive construction identifies the essential from the non-essential. The analysis is from the perspective of a "worker skilled in the art to which the patent relates as of the date the patent is published". If an essential element is different or missing from the challenged invention then there is no infringement. However, there may still be infringement where only non-essential elements are different or missing. A non-essential element is one that, from the words of the claim, are not clearly intended to be essential, or where a skilled reader would have been able