3.5 Conclusions

Today, the Big Bang model remains the most successful scientific explanation of the origin and evolution of the universe.
It aligns with the major observations — from the cosmic microwave background to the abundance of light elements and the formation of large-scale structures.

It is therefore neither irrational nor scientifically unfounded to think that the universe had a beginning — an origin point about 13.8 billion years ago, characterized by an extremely hot and dense state.
From both philosophical and mathematical perspectives, the idea of an actually infinite past presents serious difficulties: a truly infinite sequence of successive events could never be crossed step by step — yet we have clearly reached the present.
This suggests that time had a beginning and that the series of past events is not infinite. On this basis, we can state as Axiom 2 that the universe began to exist.

We have also examined why it is reasonable to think that “everything that begins to exist has a cause” — our Axiom 1.
It rests on the widely accepted principle of causality: we never observe realities coming into being without prior conditions.
In both everyday experience and scientific practice, beginnings — births, transformations, phase transitions — occur when certain causes and constraints are present.
Logically, self-causation is incoherent (what begins cannot cause itself), and circular causation explains nothing.
Quantum phenomena do not invalidate this framework: the “physical vacuum” is not nothing, and random processes (such as radioactive decay) still unfold according to laws and prior physical states.

By accepting these two axioms, the conclusion of the Kalām Cosmological Argument¹ naturally follows: the universe has a cause. This cause cannot belong to the universe itself, since it is the origin of the universe. It must therefore be immaterial, timeless, immensely powerful, and intentional. In other words, it possesses the attributes of a first cause.

Finally, it is worth invoking Occam’s razor²: when two explanations account equally well for the data, the simpler one — that which introduces the fewest extra assumptions — is to be preferred. This principle is sometimes invoked against the idea of a first cause, but it applies just as well to it: competing cosmological models that multiply unverified hypotheses (for example, certain bounce scenarios requiring ad hoc mechanisms for entropy reset) are far less parsimonious. Until robust observations demand otherwise, the standard framework — the Big Bang, possibly preceded by an inflationary phase and described by ΛCDM — remains the most economical and predictive description available. If future data were to contradict it, it should of course be revised accordingly: such is the nature of knowledge, which advances through explicit hypotheses, testable predictions, and constant confrontation with observation.

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