Common causes In part because of this economic logic, the principle of making polluters pay-of internalising the externalities, as the economists put it--is fundamental to the carbon taxes and cap-and-trade regimes for pollutants pushed by pragmatic environmentalists(for all that their more radical brethren seethe at reducing everything to calculable financial costs and benefits). Network politics are also often concerned with the issues raised by commons. The internet- means and motive for much activism-is a clear example of such a digital resource: anyone can access it under the same conditions and all traffic can, at least theoretically, be treated equally(a state which is known as"network neutrality". and a great rallying cry). But here the externalities not captured by the market are more positive than negative. Often, the more people share and use such a commons, the more they all benefit.