This principle, axiomatic as it has become, is in no way primitive, since primitive experience is sporadic and introduces us to detached scenes separated by lapses in our senses and attention. These scenes do not hang together in any local contiguity. To construct a chart of the world is a difficult feat of synthetic imagination, not to be performed without speculative boldness and a heroic insensibility to the claims of fancy. Even now most people live without topographical ideas and have no clear conception of the spatial relations that keep together the world in which they move. They feel their daily way about like animals, following a habitual scent, without dominating the range of their instinctive wanderings. Reality is rather a story to them than a system of objects and forces, nor would they think themselves mad if at any time their experience should wander into a fourth dimension. Vague dramatic and moral laws, when they find any casual application, seem to such dreaming minds more notable truths, deeper revelations of efficacious reality, than the mechanical necessities of the case, which they scarcely conceive of; and in this primordial prejudice they are confirmed by superstitious affinities often surviving in their religion and philosophy. In the midst of cities and affairs they are like landsmen at sea, incapable of an intellectual conception of their position: nor have they any complete confidence in their principles of navigation. They know the logarithms by rote merely, and if they reflect are reduced to a stupid wonder and only half believe they are in a known universe or will ever reach an earthly port. It would not require superhuman eloquence in some prophetic passenger to persuade them to throw compass and quadrant overboard and steer enthusiastically for El Dorado. The theory of navigation is essentially as speculative as that of salvation, only it has survived more experiences of the judgment and repeatedly brought those who trust in it to their promised land. [Sidenote: Its unity ideal and discoverable only by steady thought.]