The manifestation of this specific act of thought allows us to experience the relations of successiveness between conscious phenomena, and thus the temporal extensiveness, ensuring thereby the immediate continuity and the fundamental unity of conscious experience. The time of presence defines the conditions of actual experience, i.e., conscious phenomena that are immediately accessible to one's own awareness, and determines the appearance of the structural and functional unit of the stream of consciousness, namely, the episode. It corresponds to the incessantly renewed "experiential window" in which we intuit the present conscious events, but also in which we succeed in re-experiencing and pre-experiencing past and future episodes of our own conscious life.
Indeed, a fundamental assumption of Stern's theory is that perception of non-actual conscious phenomena results from their analogical and symbolical reconstitution in actual experience: past and future representational contents can be "projected" (i.e., retrieved and recombined) into the time of presence and differentiated by means of specific temporal factors, i.e., "qualities of pastness" and "qualities of futureness" respectively. The comparison in the time of presence of past, present and future events of conscious life ensures the short-term and the long-term continuity of conscious experience and the maintenance of the unity of the self through time. I first examine the 19th century psychological context of the theory of the time of presence. I analyze on the one hand the late 19th century German-speaking psychologists' reflections on the cognitive foundations of the unity of conscious experience, and, on the other hand, the 19th century program of research of time psychology and the main theoretical models of time perception elaborated before Stern's. Further to these historical developments, I propose a detailed commentary of Stern's 1897 paper on the time of presence, by showing that the cognitive model he proposes constitutes in fact a significant contribution to the theory of memory and of the stream of consciousness. Then, I propose an extensive discussion of the theoretical problems and obscurities of Stern's model, while demonstrating that Stern's reflections on the perception of the past and the future can be extended to the issue of perception of date and duration. Finally, I highlight the fact that the theoretical scheme proposed by Stern may constitute the starting point of a general model of time perception and autonoetic consciousness, in accordance with the results of current neurocognitive research on episodic memory."