The traditional nihilistic argument on the meaning of life follows the following line of thought:

  1. God and a soul are necessary for meaning in life (Extreme supernaturalism).
  2. Neither God nor a soul exists (atheism).
  3. Since God or the soul does not exist, life is inherently meaningless.

This position is now slowly replaced by newer arguments like error-theory-based nihilistic arguments on the meaning of life.

References

Metz, T. (2021). The Meaning of Life. In E. N. Zalta (Ed.), The Stanford Encyclopedia of Philosophy (Winter 2021). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/win2021/entries/life-meaning/