One of the common arguments against the idea of a First Cause of the universe or a Prime Mover is the counter argument, “What caused the First Cause? This comeback is a little like the person who, not paying attention to the details of a story being told to him by his friend, asks questions of his friend at the end of the story that belie the fact that he was not paying attention. If we are postulating a First Cause, Prime Mover, asking what caused the First Cause is nonsensical. The very definition of an un-caused, First Cause is that there is no prior cause responsible for it. If you want to posit that you believe in an infinite regressive chain of causes (multiverse, aliens from another universe, etc.) then please admit that you believe that the universe and or all of its prequels are infinite. Then, please recognize (say it out loud, perhaps) that you are embracing the turtle theory. Which is recounted nicely by Stephen Hawking in A Brief History of Time:
A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever,” said the old lady. “But it’s turtles all the way down!”
Those who reject the First Cause argument are guilty of believing in an endless supply of turtles. In this way they can push back the question of the origins of the universe and the design question.