3. Did the universe have a beginning — and if so, does it have a cause?
Since antiquity, philosophers and scientists have debated the nature of the universe: has it always existed, or did it have a beginning? Thinkers like Aristotle defended the idea of an eternal universe, without origin or end.
It is therefore clear, from all that has been said, that the whole heaven has not been created, nor can it perish, as some philosophers claim. Rather, it is one and eternal, without beginning or end, enduring for all eternity.
By contrast, other philosophical and religious traditions have argued for an origin of the universe, sometimes associated with a creative cause or force.
In this chapter, we will adopt a rigorous scientific approach (see Chapter 2) in order to retrace the major discoveries and observations that led to the Big Bang model and its modern developments (inflation, ΛCDM).
Each cosmological model — whether the standard model or alternative proposals — will be examined critically, by assessing both its explanatory strengths, its limitations, and its degree of compatibility with current observational data.
We will also examine the arguments put forward in support of alternative models, as well as the conceptual or empirical difficulties they face, in order to determine which hypotheses appear most consistent with the current state of scientific research.
In a second step, we will broaden the discussion to the philosophical level and examine whether an infinite past can be conceived rationally.
Two questions will guide our inquiry:
- Does the universe have a beginning?
- If so, can we reasonably infer the existence of a “first cause” or a creative force?
We will address these questions through the following steps:
- The Big Bang theory and alternative models
- Is it possible to traverse an infinite past?
- Why is there something rather than nothing?
- What kind of cause could create a universe?
- Conclusions
⚠️ Note to the reader: Section 3.1 is primarily scientific, while sections 3.2 and 3.4 are more philosophical in nature. If these parts feel challenging, you may skip directly to the conclusion (3.5) for a clear and accessible synthesis of the main ideas.