That's untrue; we don't know if life will develop on any planet other than Earth. We have no knowledge if life will develop in any galaxy other than the Milky Way.Assuming is a disingenuous term to use for predictability. It in itself is a question not a statement.
We already know the odds that life will develop on a planet in a galaxy is 100%.
We would have to know of life in another galaxy to claim, "the odds that life will develop on a planet in a galaxy is 100%."
That's just compounding error after error.The odds even only 1 planet will develop life in a galaxy of 400 billion stars with possibly 1600-3600 billion planets per galaxy.
Or three trillion six hundred thousand billion.
There are an estimated 125 billion galaxies.
3,600,000,000,000 x 125,000,000,000 = possible places life could have arisen.
or about 9^35th
That's a few chances life could be out there wouldn't you say?
Belief in extraterrestrial life is based entirely on faith without any scientific evidence.