The Two Times Problem: Where Is the Problem?

In: Timing & Time Perception
Michael H. Herzog EPFL School of Life Sciences: Faculté des Sciences de la Vie, Ecole polytechnique federale de Lausanne(EPFL), Lausanne, Switzerland

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offered a framework how to explain “Physical time within human time”, solving the ‘two times problem’. Here, I am asking whether such a problem exists at all. To question the question, I will appeal to neurobiological, evolutionary, and philosophical arguments suggesting that human time does not need to be reconciled with physical time.

Is there a problem? And if so, what is the problem? Intuitively, we believe that we live in a three-dimensional spatial world plus time. Einstein tells us that this intuition is wrong. There is no absolute time, independent of space. Rather, we live in a block universe where past, present, and future all equally exist. In particular, motion and change do not exist in the block universe. How can we explain the flow of time when there is no time? How can we explain the experience of motion when there is no change? Gruber et al. (2022) try to reconcile Einstein physics and our spatio-temporal experiences. The key component of their model is a basic information gathering and utilizing system (IGUS), which receives information from the world through sensors. The information is then processed both unconsciously and consciously. The IGUS has various memories for the different time points of the past, which update an unconscious component, which in turn updates the conscious component together with the current unconscious input. Thus, the IGUS has past and present represented. A major part of the paper is to identify the key temporal aspects of consciousness (flow of time, motion, persistent self, specious present, etc.) and to update the IGUS accordingly. The IGUS is updated by one ‘gadget’ for each temporal aspect and each aspect comes with a veridical gadget matching the physical aspects of the world and a corresponding gadget for our illusory experiences, which do not match physics. For this reason, the authors call their model a dualistic model. The veridical system is to guide ‘adaptive behavior’ in the physical world, the illusory system to explain our percepts.

The metaphysics of time, time perception, and the temporal aspects of consciousness are one of the most confusing topics in physics, neuroscience, and philosophy. The authors are congratulated to have opened this book with seven seals and have written a manifesto about manifest time. A complex model about a complex topic naturally produces complex comments. Here are mine.

Temporal perception: many aspects of time perception and the temporal aspects of time are under heavy debate. For example, it is an open question whether or not visual perception is discrete and if so whether it is rhythmic and if so whether it comes at a certain rate such as 10–13 Hz. In addition, there is quite some debate whether discrete perception comes with perceptual snapshots as the authors suggest or whether there is ongoing but unconscious processing (e.g., Herzog et al., 2020). However, the gadgets of the IGUS can easily be updated depending on the most current result. Hence, the proposed IGUS should be seen as an ongoing project rather than a fixed model. At the moment, it seems that the gadgets are rather independent of each other. However, most likely more complicated models are needed since many temporal aspects are not independent of each other. For example, motion processing and temporal-order processing need to interact with each other because one perceives either apparent motion of one disk or the appearance of two independent disks one after the other at different positions. Hence, motion processing and temporal-order processing seem to mutually inhibit each other, i.e., the corresponding gadgets need to be updated in tandem both in the veridical and the illusory branches. Future research will show whether this is always possible.

Regarding evolution: the veridical system matches the laws of physics to survive in the physical world, but, as I read the article, without the contributions of the illusory system (“Most important is the hypothesis that a complete veridical system contains all of the important temporal experiences to sustain the human for adaption.”). But why, then, do we have these illusions about time at all? Why do we perceive motion if there is no motion? Why did evolution come up with useless percepts, which need to be backed-up by a veridical system? I think there might be a misunderstanding about evolution in general. Evolution does not require a 1:1 veridical mapping between the external world and perception. The way we perceive the world may be an evolutionary advantage. For example, the authors are mentioning filling in of the blind spot in the eye, which seems to be a reasonable thing. String theory claims that the universe has even more than four dimensions. Maybe, four dimensions are sufficient for survival offering the advantage of more efficient computations in a lower-dimensional space. Hence, illusory perception may enhance fitness, i.e., the survival rate (Hoffman et al., 2015). But does it make sense to talk about evolution as the science of ongoing changes in order to adapt to ongoing changes of an external world, if there is no change in the block universe?

Regarding consciousness: do IGUSs have consciousness? The IGUS in their figure 1 has a box labelled C for consciousness. But a label does not make consciousness. In addition, do we want to grant consciousness to a small creature like an IGUS, which usually causes absurd consequences (Herzog et al., 2007)? Finally, the question is then, again: why do we need a conscious system when it produces only illusions. In particular, it seems that consciousness would or should be truly epiphenomenal since it would or should not contribute to behavior.

Regarding time: does an IGUS has a present? The IGUS processes past and present information but this does not mean that the IGUS has the experience of past and present information. It seems that the IGUS misses an explicit representation of time. In addition, the information about the past is in the unconscious registers, i.e., the conscious part of the IGUS does not know about them, it receives only information from them. Likewise, the authors write “Regarding the actual ‘flow’ of time” the IGUS “attributes that to the movement of information in and out of the (consciousness) register.” In other words, the experiential flow component of the FOT (flow of time) is attributed to the utilizing system of the robot and not the time of physics. But who registers the in- and outflow of information? It cannot be the consciousness system itself because it has no access to the unconscious in- and outflow.

Regarding cosmology: do we have a problem? Does space–time cosmology matter for planet earth perception? We are living in an inertial system, in which temporal order and simultaneity are physically well defined. The theory of relativity becomes only relevant for cosmological dimensions, which are not relevant for our inertial system. Newtonian physics with its three spatial and one time dimension is perfectly fine for earthly physics and perception — and much easier to compute. These simpler computations may have an evolutionary advantage (see above). Simpler representations may lead to wrong conclusions about cosmological space–time but this may come without harm for earthly creatures. For example, when we look at the starry night we believe that all stars are just out there. However, some might have ceased a long time ago while other are still there. Thus, we perceive things that are not there and we wrongly perceive simultaneity where there is none. However, these misperceptions have no impact on our daily life. Thus, is the ‘two-times problem’ really a problem?

Regarding introspection: do we experience a flow of time? When I am looking at a static red square, there is a static red square but no flow. When I am watching a soccer game, there is motion of the ball and movements of the players but there is no flow. When I am recalling childhood experiences I recall them but there is not necessarily an experience of past itself and when I am thinking what to cook for tomorrow’s dinner I have ideas about future events but no experience of future necessarily. Past, presence, and future are theoretical constructs but nothing that comes from perceptual experience. Time is a high-level construct, as is Einstein’s block universe. Thus, do we need to model a flow of time if it is only a theoretical misconstruction? It seems we are back to square one.


  • Gruber, R. P., Block, R. A., & Montemayor, C. (2022). Physical time within human time. Front. Psychol., 13, 718505.

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  • Herzog, M. H., Drissi-Daoudi, L., & Doerig, A. (2020). All in good time: long-lasting postdictive effects reveal discrete perception. Trends Cogn. Sci., 24, 826837.

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  • Herzog, M. H., Esfeld, M., & Gerstner, W. (2007). Consciousness & the small network argument. Neural Netw., 20, 10541056.

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  • Hoffman, D. D., Singh, M., & Prakash, C., (2015). The interface theory of perception. Psychon. Bull. Rev., 22, 14801506.

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