(_c_) _Abstraction._ The part played by abstraction in the formation of the conceptual space and time order out of the data of perception is often overlooked by theorists, but is of fundamental importance, as we shall see immediately. We have already learned that the most significant fact about the time and space order of individual experience is that its directions are _unique_, because they radiate out from the unique _here_ and _now_ of immediate feeling. In the construction of the conceptual space and time order we make entire abstraction from this dependence on the immediate feeling of a subject. Conceptual space contains an infinity of positions, but none of them is a _here_; conceptual time an infinity of moments, but none of them is a _now_. As the time and space of the conceptual order are taken in abstraction from the differences between individual points of view, no one point in either can be regarded as having more claim than any other to be the natural “origin of co-ordinates” with reference to which directions are estimated. We shall have repeated opportunity in the remainder of this chapter to observe how important are the consequences of this abstraction. Abstraction also enters in another way into the construction by which conceptual space and time are created. Actual perceived space and time are indeed never empty, but always filled with a content of “secondary” qualities. In other words, they are always one aspect of a larger whole of fact. Extension is never perceived apart from some further visual or tactual quality of the extended, temporal lapse never perceived without some change in presented content, however slight. But in constructing the conceptual space and time system, we abstract altogether from this qualitative aspect; we think solely of the variety of positions and directions in time and space without taking any account of the further qualitative differences with which they are accompanied in concrete experience. Thus we come by the notion of an _empty_ space and an _empty_ time as mere systems of positions into which various contents may subsequently be put. Strictly speaking, the notion of an empty space or an empty time is unmeaning, as the simple experiment of thinking of their existence is sufficient to show. We cannot in thought successfully separate the spatial and temporal aspects of experience from the rest of the whole to which they belong and take them as subsisting by themselves, any more than we can take timbre as subsisting apart from musical pitch or colour-tone from saturation. We can, however, confine our attention to the spatial-temporal system of positions without taking into account the special secondary properties of the extended and successive. It is from this logical abstraction that the illusion arises when we imagine an empty set of spatial and temporal positions as having first to exist in order that they may be subsequently “filled” with a variety of contents.[146]