No one can own an idea. Thus creating something like a property right over intangible assets is a meaningless endeavour. Doing so gives monopoly power to individuals who may not make efficient or equitable use of their inventions or products. Physical property is a tangible asset, and thus can be protected by tangible safeguards. Ideas do not share this right to protection, because an idea, once spoken, enters the public domain and belongs to anyone who can use it.