Time, as we experience it, seems undeniable: it flows, leads life, and shapes reality. Still, for a long time, philosophers and scientists have been engaged in discussion: does time really represent an objective feature of the world, or is it just an illusion created by human perception? Is it something that stands independently by itself, or is it just a concept that we project with our minds onto the world to structure reality?

Saint Augustine, in his Confessions, asks, “What is time?” He realized that, although everyone seems to understand time, he cannot explain it. In fact, for Augustine, the reality of time is closely connected to human consciousness: the past is but a memory, the future is an anticipation, and the present is but an instant. In this respect, time is not an independent entity; it is something that arises in our minds.

Another great philosopher who regarded the reduction of time to simple measures with skepticism was Henri Bergson. His concept of “duration” divided time into a quantitative aspect, measured by clocks, and a qualitative one, the real-time experience of it. In this scientific view, time becomes an artificial unit, while real time is flowing, continuous, and deeply linked to consciousness.

Immanuel Kant added another dimension to this view by asserting that time, along with space, is not an objective feature of the external world but a condition of human experience. In his Critique of Pure Reason, Kant argued that time is a necessary framework that our minds apply to reality to organize our sensory perceptions. We cannot experience the world outside of time, but that does not mean time exists independently of us.

More recently, modern physics has brought new interest to this debate. Albert Einstein, with his theory of relativity, completely changed the concept by proving that time is relative to the observer and to gravitational fields. Time can expand or contract; events that we sense as part of continuous time may, in fact, be elastic and highly alterable in their duration. A variation of this idea is the “block universe” theory, introduced by philosophers such as Hermann Minkowski, which suggests that the past, present, and future all coexist in four-dimensional spacetime. From this perspective, the flow of time is a human illusion; all moments exist together, but we experience them sequentially because our perception is limited.

The philosopher J.M.E. McTaggart took this point even further, and in The Unreality of Time, advanced the position that time itself is self-contradictory. McTaggart argues that a time conceived as an A-series — that is, past, present, and future — embodies a logical contradiction and is therefore unreal. His clear differentiation between the A-series and B-series reveals that the intuitive understanding of the concept of time is essentially flawed.

Today, some scientists, such as Carlo Rovelli, suggest that time is perhaps an emergent rather than a fundamental property of reality. Rovelli states in his book L’Ordre du Temps that the “now” is merely derived from the interactions of particles. This perspective is reminiscent of philosophical positions asking whether time really passes or even exists as a physical entity outside human observation.

Thus, whether real or illusory, time remains a question that existential reflections from Saint Augustine, transcendental deductions from Kant, and revolutionary discoveries from Einstein seem to raise when considering a complex and multifaceted phenomenon. Be it the reality of flowing time or just a concept shaped by human experience, it continues to challenge our deepest understanding of existence.

I believe that a satisfactory conceptualization is one that can be explained to and satisfy a five year old, who will then spend the rest of their life finding it to be correct.

Can we give consensus to this definition?

Time is an artificial measure of our sense of duration. Experiencing duration is the primary motivation driving the continuous creation of now.

The question reminded me of an article I read long time ago, which said that time is what people created to explain the changes in the environment (seasons) and to make a system which would facilitate the communication and meetings easier (imagine how to schedule a meeting if there is no concept of time?).