262 HARVARD LAW REVIEW Manifestly, what is true of property used in interstate commerce is equally true of business that is interstate commerce. If such business is exempted from burdens which local business has to bear, it is thereby given a bounty to the extent of the exemption. Mr. Carter's point is that a tax is not a burden on interstate commerce unless it discriminates against that commerce. It would probably be safer to say that such burden on interstate commerce as non- discriminatory taxation may impose is not sufficiently serious to be accounted a regulation. Such taxation is forbidden by no explicit language in the Constitution. The exemption of interstate com- merce from state taxation arises by implication only, and the im- plication should not be carried to the point of compelling the states to confer positive benefits on interstate commerce by discrimina- tions in its favor. Mr. Carter apparently appreciated the applicability of his con- cession to taxes on business, for he hastens to add that "a tax in any other form [than a tax on property] cannot be thus equalized over all private interests, and, if allowed, would be, or might easily be made to be, an especial burden." "^ Here is the crucial difficulty in the problem. In Ohio, express companies were taxed on the basis of their income-producing capacities, while many other businesses were assessed on a less onerous basis. Was there not therefore necessarily a discrimination against the express companies and the interstate commerce which they carried on? In one sense, of course, there is always discrimination, wherever there is difference of treat- ment. The requirement of absolute uniformity is, however, utterly impracticable. The rule of "reasonable classification" which the court has been compelled to adopt in applying the equal-protection clause "^ seems necessary also in passing upon issues of alleged discrimination raised under other constitutional clauses. But the Express cases were wisely decided only if they can be brought within the rule of reasonable classification. The theories of both the majority and the minority avoided explicit analysis of this element in the situation. Chief Justice Fuller quoted a portion of the opinion of the state court which made the point that the earning capacity of real estate determines its assessable "8 i6s U. S. 194, 218, 41 L. Ed. 694 (1897). "' See Missouri v. Lewis, loi U. S. 22 (1879).
