Nothing could be further from the truth. The argument that the universe had a beginning is called the "kalam cosmological argument", and was developed by Muslim philosophers. Aquinas was well aware of this argument, and rejected it because he did not think it could be proven philosophically that the universe had a beginning. Aquinas said: "By faith alone do we hold, and by no demonstration can it be proved, that the world did not always exist..."
If the kalam cosmological argument could be said to be arguing for a "knocker down of the first domino", the First Way could be said to be arguing for "the motor that drives the watch". No matter how old the watch is, as long as it's hands are turning there must be a motor inside it.
Misconception #2: Aquinas does not have good reasons for thinking there cannot be an infinite chain of causes
Much of this stems from the above misconception. Once it is understood that Aquinas is arguing for a present source, and not a finite past, it can be easily shown why he thinks an infinite chain is impossible. Consider first how a receiver necessitates a giver:
- Receiver <--------- Giver
- Receiver <-------------------------------------------------------------------------
In which case, again, the receiver would not be receiving anything.
This is what Aquinas means when he says: But this cannot go on to infinity, because then there would be no first mover [giver], and, consequently, no other mover [receiver]...
Misconception #3: Aquinas stuffs "God" into a gap in our scientific knowledge.
God-of-the-gaps reasoning is when there is a gap in scientific knowledge, and someone says "God did it!" In other words, they stuff God as an explanation into the gaps in our knowledge. Sometimes it is alleged that Aquinas didn't know how our universe began, and so he just stuck "God" into that gap.
But first of all, Aquinas was not arguing for a beginning to the universe, as can be seen above. Second, his argument is deductive. It argues from the premises that things are changing and that nothing can change itself, to something that can cause change without having to be changed by anything further. Much the same you might reason that the lamp in your living room is receiving electricity from the outlet, which is in turn receiving electricity from the power lines, and so on to the existence of something that can give electricity without having to get it from anything further. That is, a power plant.
Similarly, the argument is trying to argue from the fact that nothing can change itself, and so must be receiving change from somewhere else, to a source of change that does not need to receive change from anything further. The argument may or may not be sound, but it proceeds logically via deductive argument to a necessary conclusion. It is not trying to arguing for the best explanation for a set of facts, as it would be if it were guilty of god-of-the-gaps.
Misconception #4: Aquinas is specially pleading for God, exempting him from the rules of earlier premises. He says that everything has a cause, but then goes on to exempt God from needing a cause.
He never says everything needs a cause, or even that everything is in motion. Again, we might say that the lamp must receive electricity and then reason that there must therefore be a source of electricity, and we would not be specially pleading for the source. The source by definition cannot be receiving electricity from anything further because then it just wouldn't be the source. And a receiver necessitates a source.
Misconception #5: Aquinas gives no reason to think that this first cause must be God; it could be Zeus or Ishtar or anything else.
The argument concludes with something of "pure actuality". That is, something with no potentials for change. He spends much of the first part of the Summa Theologica arguing for why something of pure actuality must have certain familiar attributes. For example, he argues that something that is purely actual must be immaterial, because matter and energy all have the potential to change. But something that is purely actual does not have any potentials. Also, since it is the cause of all change, then it is the cause of anything that has happened or ever will happen, and so it is all-powerful. He goes on to show why it is also all-knowing, all-good, and so on. So whatever one wishes to name it, the argument is for a singular, immaterial, all-knowing, all-powerful, all-good entity.