The idea that information is not (or should not be) ownable, and subject to buying or selling. The background of this idea is that no information is created out of a vacuum; no matter what you create it is always based of previous information. You are standing on the shoulders of giants, as it were, and it would be presumptious to say the least to assert this your derived information as your property. The very term intellectual property is an oxymoron.
Another reason why information should not be owned, is that there is no need for it. Ordinary objects exist in limited quantities, and there is a certain cost associated with duplicating. For (digital) information however, the duplication cost is basically zero. Because of this, there is no reason why not everyone should have unlimited and free access to information.
See also Information wants to be free.