The most common objection to fine tuning arguments for theism is that there are, or might be, multiple universes among which the fundamental physical constants and parameters vary. This essays describes the two main variants of this objection and argues that they both fail.
Collins, Robin, "The Many-Worlds Hypothesis As an Explanation of Cosmic Fine-Tuning: An Alternative to Design?" (2006). Philosphy Educator Scholarship. 5.