In order to understand this whole problem it is necessary to bear in mind certain cardinal principles of our constitutional law. All corporations, with the exception of national banks, two or three railroad companies, and the Panama Canal, have been and are creatures of the State, not, as yet, of the Federal government, which can only create them for purposes specifically delegated to it and not merely for private profit. The power to create corporations is essential to sovereignty, and the sovereign may decline to recognize all but its own corporations. Under the doctrine of comity, such corporations can act in any other State with all the powers given them in the State where they are created, except only they be expressly limited by a statute of such other State. They may, however, be entirely excluded; only not to the destruction of property rights once acquired. On the other hand, corporations conducting interstate commerce may not be excluded or such business interfered with by State legislation. The writer was for four years counsel to the Industrial Commission at Washington and one of the commissioners appointed to draw the present business corporation law of Massachusetts. In both such capacities he had the advantage of hearing the expert opinions of many witnesses. There were two, and only two, broad theories of legislation about private business corporations: One view, the older view, that they should be carefully limited and regulated by the State at every point, and that their solvency, or at least the intrinsic value of their capital stock, should, as far as possible, be guaranteed by legislation, to the public as well as to their creditors and stockholders; and that for any fraud, or even defect of organization, the stockholders, or at least the directors, should be liable. On the other hand, the modern view, that it was no business of the public to protect investors, or even creditors, and that the corporations should be given as free a hand as possible, with no limitation as to their size, the nature of business they are to transact, or the payment in of their capital stock. This is the corporation problem. The State-and-Federal problem may be called that other difficulty which arises from the clashing jurisdictions of the States among themselves and with the Federal government, their laws and their courts, as to the corporations now created, particularly railroads and corporations "engaged in interstate commerce" which may include all the "trusts," if the mere fact that they do business in many States makes them so.