In addition to the arguments drawn from geography and economic needs were others no less cogent. Union was imperative for defence. Political weakness was always a tempting bait to a neighbouring power. The great resources of the British colonies combined with their lack of unity might well induce the American republic to attempt conquest. Especially was the St. Lawrence waterway tempting to the United States, since in the course of time it must become the shipping route for the wheat harvests of the West. The power in possession of it would control the chief roadway to the grain fields. In addition the colonies had other resources for which union alone could give adequate protection, rich fisheries, extensive forests, fertile lands. "Facts are logical, and unless we dream that the laws of cause and effect will be suspended in our favour, we must look either to the internal union or the political extinction of these provinces at no distant day." Not merely would the wealthy natural resources of British North America be preserved, but they would best be developed by the consolidation of the colonies into one state. With such a system McGee looked forward to Canada possessing, by the close of the century, 25,000,000 people. Moreover, he anticipated the appearance of all the other more brilliant, if less tangible, accomplishments of national life, which had difficulty in arising under the existing political disunion, a native literature, with developments in art, science, and philosophy. McGee went further than marshalling arguments for union. He described in general terms the nature of the constitution suitable for the colonies. He considered it neither desirable nor possible that the various provinces with their diverse geographical characters and economic interests should be fused into one political unit. "Our river system indicates our union, railroads and canals will strengthen these natural bonds, but complete oneness of political life must still be wanting to sea-beaten Newfoundland and the wheat-bearing West." The same geographical facts which pressed the need of union made the recognition of local autonomy imperative. The new constitution must be federal, allowing a large measure of local autonomy, while constituting a central government to deal with common interests. Many of the leading Fathers of Confederation, most prominent among whom was Sir John A. Macdonald, began with the suggestion of a legislative union, and only with reluctance in the heat of constitution-building recognized the need of federal institutions. But with keen insight McGee saw from the outset that only federation could be the goal of British Americans. Provincial governments with the recognition of certain provincial rights would be a guarantee of liberty in the new state.