§ 4. Time as Ideal Construction. — The process of ideal construction makes a greater difference in the case of time than even in that of space. We have seen how in an ideally represented timeseries the distinction between now and then, or between one now and another, becomes relative, so that according to the point of view we may regard any part of the series as a now, and what precedes or follows as relatively future or past. But besides this relative antecedence and subsequence, there is also what we may call an absolute now, — the moment of present sensation. Present time in this sense is not merely defined by its relations, but has a special stamp or mark upon it, constituted by its sensuous vividness and definiteness. It thus forms a fixed startingpoint for ideal construction of timeorder. What is prior to it is regarded not merely as relatively but as absolutely past; what is subsequent to it is regarded not merely as relatively but as absolutely future. Past and future are still defined only by their relations; but the startingpoint from which we define them is not arbitrary but fixed, and fixed not by ideal construction but by actual sensation. As Dr. Ward says: " To a being whose presentations never passed through the transitions which ours undergo — first divested of the strength and vividness of impressions, again reinvested with them and brought back from the faint world of ideas — the sharp contrasts of 'now' and 'then,' and all the manifold emotions they occasion, would be quite unknown. ... In the obligation to wait and work in hope or dread of what is 'still to come' there is much more than timeorder."*

* Article "Psychology," Encyclopaedia Britannica, ninth edition, xx., p. 64.

The apprehension of past and future in this absolute sense presupposes a startingpoint in the immediate sense experience of the moment; and an ideal construction in two directions, on the one hand, of what has preceded, on the other, of what is to follow, the actual now. On the whole, anticipation of the future must be regarded as prior in the order of development to reminiscence of the past. For the primary stimulus to ideational activity comes from practical needs; and these are in the first instance concerned with the future. Given a present urgency in the way of hunger or thirst, the primary demand made upon ideational activity is for the devising of means to procure food or drink. It is thus called on to follow out a train of ideas representing the successive links connecting the present state of need with a future state of satisfaction. Trains of ideas representing previous sequences of events will at first be called into play mainly by the need for data derived from the past to use in providing for the future. But the grand stimulus to reminiscence is not to be found in dealings with the physical world, but in the personal and social interests which we shall have to discuss under the head of Self-Consciousness. There are two characteristics which distinguish the future from the past apart from abstract priority and subsequence. The future is uncertain, or in other words, its anticipation may take the form, not of one definitely fixed series of ideal representations, but of a number of alternative lines, which compete with each other for predominance in consciousness. But the past has already taken determinate form; in it one definite alternative has already been selected to the exclusion of others. Besides this, past and future have an altogether different relation to practical activity. The future is something which may be in a greater or less degree determined by the agency of the subject himself; and he must be continually adjusting his actions so as to modify it, if he is to survive and live a tolerable life in the world. But the past is beyond his control. Retrospection can only be of use in supplying data for prearranging the future.

So far we have considered only the lapse of time as it appears to the individual subject, or in other words what is sometimes called subjective time. But it is plain that this does not coincide with time as measured by the clock. Shakespeare tells us that time travels "in divers paces with clivers persons"; Newton tells us that time moves at a constant rate. Shakespeare's time is evidently subjective time, and Newton's objective time. In a position of great difficulty and danger minutes may appear like hours. Two lovers in the enjoyment of a lovers' conversation may find hours pass like minutes. The subjective estimate of time is different from time as measured by the clock. Objective time as distinguished from subjective is a product of ideal construction. The beginning of the process by which it comes to be conceived is found in the conditions of practical activity. Lapse of time is often an important factor in the attainment of practical ends. It takes a certain time, for instance, to travel from one given place to another, or to cook a piece of meat, or for water to boil, or for clay to harden in the sun. Now in practical calculations it will not do to leave the estimate of the lapse of time in such cases to the varying impressions of the individual. The only effective mode of procedure is to find some other process which coincides in its beginning and termination with the process of which the duration is to be measured. Thus, if the question be, how long it takes to get from one place to another, a sufficient answer may be found by reference to the course of the sun. It will take perhaps from sunrise to sunset of a summer's day; or from sunrise till noon. The efficiency of this mode of procedure depends upon the discovery of uniform standards of measurement. These are best supplied by rhythmic processes which repeat themselves at intervals. If it is found that the duration of events in general can for practical purposes be defined by saying that they take the same time as one or more repetitions of a certain rhythmic process, this process has proved its efficiency as a standard of measurement. The process which we now most commonly use is the movement of the hands of a clock. The movement of the minutehand, starting from one position and returning to it again, constitutes a fixed period which we call an hour. So the movement over a smaller interval on the dial constitutes another fixed period which we call a minute. Objective time is thus an ideal construction, and the principle on which it rests is that processes otherwise similar, and taking place under similar conditions, will occupy the same time. Thus if they start simultaneously, they will terminate simultaneously, and so on. Similarly, if two dissimilar processes are found to occupy the same time on one occasion, they will occupy the same time on another occasion, under like conditions.