The European Union is attempting to pass a Directive that will force many European governments to permit patents on software despite growing protests from software engineers and small European software companies. Opponents fear that software patents will stifle innovation and competition in their industry, increasing their legal costs, while leaving them at the mercy of large companies who have the resources to acquire large numbers of patents. The Directive is supported by trade groups dominated by large multinational software companies, along with national patent offices who generate revenue from patent applications.A patent is a fearsome weapon, not only does it prevent someone from copying an invention, it also prevents them from independently inventing the same thing. This means that you could spend your entire life sitting in a cave, with no contact with the outside world, and anything you invent could still infringe other people’s patents. In contrast, a copyright only prevents other people from copying your work. If you copyright a poem and someone else, by chance, happens to write the same poem without copying yours, then they are not infringing your copyright.The purpose of patents, indeed all forms of intellectual property, is to promote the arts and sciences. Patents achieve this by granting an inventor exclusive control over their invention for a limited time. In return, the inventor is required to disclose their invention so that after the limited time expires, it is freely available to the rest of society. Society benefits when this provides an incentive for inventors to invent, where otherwise they might not have bothered.A patent isn’t just granted on an idea for an invention, it can only be granted once you have a prototype, or at least the ability to teach someone how to build a prototype, this is known as a “teachable invention”. Patents therefore motivate an inventor to take their idea and invest the time and money to develop it into a teachable invention. In return for this, and a small fee, inventors are granted a 20 year monopoly over their invention.This monopoly is not granted without a price. Every invention builds on those that came before, yet for the duration of a patent nobody else can build on a patented invention without the permission of the inventor. This creates a cost for society, and other inventors. Patents work when the benefit to society of having the invention outweighs the cost of the inventor’s monopoly over it.In a field such as pharmaceuticals, a vast investment may be required to get from an idea for a new drug, to the drug itself. In this case, it is easy to see how a patent on this drug will benefit society if it provides sufficient motivation to the drug’s inventor to make the investment required to invent it.Software, however, is very different. Getting from an idea to a prototype in software requires very little investment and risk. This is the great strength of software. Its why Bill Gates, a college drop-out, could build a multi-billion dollar company out of nothing but the ideas in his head. Its why Linus Torvalds could later sow the seeds of an operating system built by volunteers that would challenge that multi-billion dollar company.Patents should not apply to software for the simple reason that they would do far more harm than good, harming creativity rather than promoting it. Software doesn’t need patents, copyright is more than adequate to provide the incentive software engineers need to turn their ideas into software. The cost to society of a 20 year monopoly over a software invention will never be justified, because it is inconceivable that any software invention could require such a powerful incentive. The price for this monopoly is paid by other inventors, and so the effect is to stifle innovation, not to promote it.Unfortunately software is not the only field where patents do more harm than good. Those advocating software patents often ask “Why should software creators be denied patent protection, while those in other fields are not?”. This begs the question. When patents do more harm than good, as they do in software, patents do not afford protection, rather for most software creators they are a threat. One should therefore ask “Why must software creators endure patents just because those in other fields do?”.