Over the years I've put up numerous posts on what's called cosmic fine-tuning, i.e. the idea that the forces, parameters and constants that make up the fabric of our universe must be exquisitely fine-tuned to unimaginable precision in order for the universe to be life-permitting.
The fact of fine-tuning is such strong support for the belief that the universe is the product of an intelligent designer that those who wish to evade that conclusion have been forced to come up with some pretty desperate counter hypotheses to rebut it.
One of these is the multiverse hypothesis, the idea that there are an infinity of other universes, all different from each other. Given the assumption then a universe like ours, no matter how improbable, must exist. See here and here)
Another response to the fine-tuning phenomenon is what's called the Weak Anthropic Principle (WAP).
WAP proponents argue that the fine-tuning of the cosmos isn't anything to marvel at since if the cosmos wasn't fine-tuned no life would exist and we wouldn't be here to observe it. This argument sounds very peculiar, but it may be difficult to see exactly what's wrong with it. In fact, a number of very bright people have embraced it, but its popularity began to wane once philosophers began to give it some thought.
This eight minute video by Inspiring Philosophy explains why the WAP is more like a scientific card trick than a plausible scientific theory:
