The Commons as a term may have once referred to central park-lands in cities which the whole community owned. In modern usage, it refers to property, resources, ideas, traditions and heritage of a State or Nation or even the inhabitants of the whole World. Extreme Conservatives and Neoliberals are antagonistic to Public or Common ownership, and see any continuation or defense of common property as an unjust interference with their liberties.
Liberals, and most sane people for that matter, understand that the commons, especially our environment (our actual physical environment, economic environment, and social environment), belong to all of us, and that we have a duty to preserve and protect it and an absolute right to prevent others from degrading it, and that we have the right not only to choose how it's used, but to demand payment for the use of it. If that means that we institute a method of taxation which seeks payment based upon costs or benefits gained from our mutual property, it's our right to do so.