We explore the meaning of time by studying the notions of time inherent in the different physical theories, the different representations we have built of Nature, notably: Classical Mechanics of Newton, Special and General Relativity of Einstein, Quantum Mechanics, Cosmology, Complex Systems, String Theory, Quantum Gravity. We notice that the notions of time, originating from the different physical theories, are not identical. They range from absolute, rigid specifications of time, to internal, relational considerations of time. Considering a physical system as an information-processing system, we link time to the generation of information and innovation. We contrast the concepts of time derived within Modern Science to Peirce’s evolutionary metaphysics and Whitehead’s process philosophy. We attempt to bypass the old dichotomy being-becoming, by indicating the need for an “ontology in the temporal”, and suggesting temporality as a mode of existence (τρόπος υπάρξεως) of being.

Dynamical systems in classical, relativistic and quantum physics are ruled by laws with time reversibility. Complex dynamical systems with time-irreversibility are known from thermodynamics, biological evolution, growth of organisms, brain research, aging of people, and historical processes in social sciences. Complex systems are systems that compromise many interacting parts with the ability to generate a new quality of macroscopic collective behavior the manifestations of which are the spontaneous emergence of distinctive temporal, spatial or functional structures. But, emergence means no mystery. Mathematically, the emergence of macroscopic features results from the nonlinear interactions of the elements in a complex system. Complex systems can also be simulated by computational systems. Thus, arrows of time and aging processes are not only subjective experiences or even contradictions to natural laws, but they can be explained by the nonlinear dynamics of complex systems. Human experiences and religious concepts of an arrow of time are considered in a modern scientific framework. Platonic ideas of eternity are at least understandable with respect to mathematical invariance and symmetry of physical laws. But Heraclit’s world of change and dynamics can be mapped onto our daily real-life experiences of arrow of time.

Within the framework of General Relativity, a universal cosmic time that is relevant for all observers who are commoving with the cosmic substratum can be established by a convenient system of coordinates. However, this is only possible, if the substratum is free from vortices, in accordance with the so-called “Cosmological Principle”. Hence, the existence of a cosmic time depends on contingent properties of the cosmic substratum. – Only if these properties are given, the age and the dynamical behavior of the universe can consistently be described. Under this assumption, we discuss the question, whether the universe could have an infinite past and show that – in spite of a long lasting philosophical debate from Proclus to Kant - there are consistent physical models with infinite age. Furthermore, we argue that the concept of eternity, as it was conceived in the philosophical tradition, can be given an adequate meaning within the context of modern relativistic cosmology. Also this problem can be traced back to ancient Greek philosophy and will be discussed in detail.

The original formulation of the (weak) anthropic principle was prompted by a question about objective time at a macroscopic level, namely the age of the universe when “anthropic” observers such as ourselves would be most likely to emerge. Theoretical interpretation of what one observes requires the theory to indicate what is expected, which will commonly depend on where, and particularly when, the observation can be expected to occur. In response to the question of where and when, the original version of the anthropic principle proposed an a priori probability weighting proportional to the number of “anthropic” observers present. More refined versions would adjust this by an anthropic quotient allowing for the relative rate of subjective (sentient) mental processing (which would presumably have been lower in extinct hominids than in modern humans). The present discussion takes up the question of the time unit characterising the biological clock controlling our subjective internal time, using a revised alternative to a line of argument due to Press, who postulated that animal size is limited by the brittleness of bone. On the basis of a static support condition depending on the tensile strength of flesh rather than bone, it is reasoned here that our size should be subject to a limit inversely proportional to the surface gravitation field g, which is itself found to be proportional (with a factor given by the 5/2 power of the fine structure constant) to the gravitational coupling constant. This provides an animal size limit that will in all cases be of the order of a thousandth of the maximum mountain height, which will itself be of the order of a thousandth of the planetary radius. The upshot, via the (strong) anthropic principle, is that the need for brains, and therefore planets, that are large in terms of baryon number may be what explains the weakness of gravity relative to electromagnetism.

A notion of biological time can be derived from distinct physiological ‘units of becoming’, by which an organism recreates itself in individual acts of experience. Using this starting point we present characteristic features of biological time in lower organisms. In these organisms the irreversibility of every act of experience can be attributed to a sequence of physiological processes of specific duration, termed “adaptive events”, in which energy converting subsystems of a cell interact with the changing environment. In this process, the subsystems pass, via an adaptive operation mode, from one adapted state to the next. In adaptive operation modes alterations of the environment are ‘interpreted’ in the light of former experiences. Thereby, the subsystems are reconstructed according to these interpretations such that the resulting adapted state potentially allows optimal performance of the organism in the future. In this regard adaptive events contain a temporal vector character in that they connect former with future events and establish the irreversible historicity of the life process, in which information pertaining to the self-preservation is transferred from one adaptive event to the next: the latter “inherits” the results of former interpretations. By appropriating it selectively, it is entering into a future in which its own interpretation is passed on to the following adaptive event. This system-theoretical line of reasoning is elaborated in detail using an example from aquatic ecology. In a generalization for higher organisms the temporal vector character of adaptive events is related to basic propositions of Whitehead’s process philosophy and to the time concept of Augustinus.

People get accustomed to the experience of time. An almost constant movement from the past towards the future appears psychologically inevitable and similar to gravitation, which physically and inevitably appears to pull us towards the center of the earth. This contribution describes conditions which change the perception of time; Alzheimer's disease, which eliminates the recent past; frontotemporal dementia, which diminishes curiosity, fear, and further future concerns; and delirium with a loss of a laminar stream of consciousness or time. It may be a coincidence that brain structures primarily dealing with the past rest in the back of the head, while structures considering future prospects sit in the frontal lobe, and a laminar processing of the present relies on an intact central brain structure. Even though physical time may continue as usual, its perception and validation is subject to cerebral distortions.

Phenomenological analyses and questionnaire studies have shown that changes in time experience are a prominent feature of mystical states of consciousness. Spiritual traditions employ a variety of methods to induce these states. Research on meditation and psychedelic drugs can help to identify involved brain mechanisms and neural correlates of mystical states. A theory is presented that explains the experience of unity and timelessness with a phase transition to extended coherent EEG gamma activity. Based on this theory, ascetic and meditative practices can be understood as rational methods to enable qualitative shifts in the large-scale organization of brain dynamics. Some supporting evidence for the theory comes from a study with Buddhist monks. Research on mystical experiences has to deal with many methodological challenges and requires a close collaboration of scientists and religious practitioners. Research of this kind can yield important insights into the relativity of reality and its relation to brain functioning.

In the present paper we examine different forms of time, focusing especially on the relation between the objective time and time of subjective experience. Experimental data from psychophysical studies on duration perception are presented, and the ‘dual klepsydra model’ of internal time representation is introduced. Relevant notions of abstract chronometry are briefly reviewed, and properties of time-scales generated by ‘klepsydraic clocks’ are studied. It is shown that these time-scales allow for a consistent time-keeping, although they are non-uniform with respect to the objective time. Parallels between our findings and E.A. Milne’s theory, revealing plurality of cosmological time-scales, are pointed out. Unitary and uniform time-scale then appears as an intersubjective construct, arising from communication of shared phenomenal fields by an ensemble of observers. Limits of the presented approach, encountered at the asymptote of cosmological and theological thought, are drawn.

The essay intends to clarify the ontological status and validity of time as such, as well as the modes of time (past, present, future) and to relate them to God’s eternity. The famous analysis of time and time-experience given by Augustine serves as a starting point to demonstrate the questions at stake for a theological reflection on the relation between time, human existence and eternity. The author then argues for the ontological significance of the passage of time and thus for the eternal significance of transient human existence by referring to physical cosmology and the philosophical concept of presentism. System theory and semiotics allow for further clarification of the status of temporal processes for the development of human existence and selfunderstanding. In that context, religion is seen as a means not to step out of time, but to form and devise human temporal existence for individuals and communities. Finally, the Christian triad of faith, hope and love is mapped to the Augustinian categories of memory, expectation and attention, thus providing the hermeneutical key for an eschatological perspective of human existence.

Is time a matter of consciousness only or can it draw upon reality? Not only since Augustine’s question “But then what exactly is time?” the status of time has been challenged, but also much earlier during the days of the Ancient Greek philosophers. They already realized that the question of time must be confronted with the thought of eternity. For them, it was without question that eternity is the transcendental background of time. The insights of modern physics force us to reconsider 1. the meaning of time and its status of reality; 2. the relationship between absoluteness and relativity of time; 3. the idea of an eternal universe and the eternity of time.

This paper raises the question of a possible combination of eternity and time. Only if both aspects can coexist, we will be able to keep the idea of human freedom. In spite of a common prejudice, an eternal universe and its deterministic natural laws do not interfere with freedom as long as time plays a substantial role in our general rules of operation. Moreover, determinism plays an even necessary role, because it is only within determinism that a rational concept of freedom in terms of following rules can be maintained. It is time, which saves the freedom of the human will in spite of and even because of the determinism of natural laws.

Therefore, eternity and determinism do not contradict the freedom of will. However, it deserves an ontological concept of time, which is founded on a concept of eternity, not being “timeless” but also bearing time.

This paper addresses three issues. In the first part the relation between consciousness and time is being discussed as it developed in the history of philosophy and theology. It covers Plato, Plotinus and St. Augustine. It continues in the second part to describe that time it is being perceived in the mystical consciousness as eternity which means in this context timelessness. Examples from world religions are offered. The question is asked if this eternity in mystical experience can be understood as relating to the eternity of God or as a mere self-experience. In order to settle this question mystical experiences as being interpreted from the angle of modern neuroscience as the result of self-organizing processes of meditation that can be described as attractors. In the final third part it is suggested to discern the eternity of mystical states of mind as timelessness from eternity as an attribute of the triune God.