§ 4. _Characteristics of the Conceptual Time and Space Order._ The following characteristics of the conceptual space and time created by the construction we have just examined, call for special notice. Conceptual space and time are necessarily taken, for reasons already explained, to be _unlimited_, and _indefinitely divisible_. Though it does not seem inevitable that they should be _continuous_, we appear to be unable to attach any positive meaning to the notion of their discontinuity, and, in the practical need for the application to them of the complete number-series, we have a valid positive ground for taking them as continuous. But space and time are thus resolved, in the process of their conceptual construction, into _continuous infinite series_ of which the terms are spatial and temporal positions or points. Unlike the _parts_ of perceptual space and time, these conceptual terms are not themselves spaces or times, as they contain no internal multiplicity of structure. Conceptual space and time are thus not wholes or aggregates of parts, but systems of relations between terms which possess no quantitative character. Between any two terms of the spatial, or again of the temporal, series there is one unique relation, which is completely determined by the assignment of the terms, their _distance_. In the temporal series, which has only one dimension, you can only pass from any one given term to any other through a series of intermediate terms which is once and for all determined when the initial and final terms are given, hence nothing is required beyond the terms themselves to fix their distance. The spatial series is multi-dimensional, _i.e._ you can pass from any one term in it to any second by an indefinite variety of routes through intermediate terms, but it is still true that there is one and only one such route which is completely determined when the terms in question are known, namely, the straight line passing through both. This straight line constitutes the unique _distance_ of the two points from each other.[147] Thus the genuine concept of which those of space and time are species is not that of _magnitude_ or _quantity_, but of _serial order_.