John Marshall Harlan II

“ As I read the cases the existence of some income from intrastate business on the part of the taxed corporation, while sometimes adverted to, has never been considered essential to the valid taxation of such 'interstate' income. The cases upholding taxes of this kind cannot, in my opinion, properly be said to rest on the theory that the income earned from the carrying on of interstate commerce was not in fact being taxed, but rather was being utilized simply to measure the income derived from some separate, but unidentified, intrastate commerce, which income was in truth the subject of the tax. ”

“ There the Court explicitly recognized that the question before it was whether net income from exclusively interstate commerce could be taxed by a State on an apportioned basis together with other income of a corporation. ”

“ In each case the amount of the tax will increase as the profitability of the interstate business done increases. This Court has consistently upheld state net income taxes of general application so applied as to reach that portion of the profits of interstate business enterprises fairly allocable to activities within the State's borders. We do no more today. ”