The uncaused cause of the universe is a subject of interest to the philosophy of religion and metaphysics. However, I have not yet encountered a satisfying set of necessary conditions for something to be the so-called "uncaused cause".

The definition that I have encountered the most is that it must have existed from eternity until at the beginning of the universe or after, however I take issue with this definition. That is, it does not not rule out the possibility of an infinite causal chain. An infinite causal chain must, by definition, exist since eternity, as every time you ask what is the cause of one event you'd go back further in time, because a cause must happen before its effects, and in order for it to be infinite, it must have no end, therefore an infinite causal chain is a possible candidate for an uncaused first cause.

So, what do you think ? What is necessary for something to be the "uncaused first cause" ? Do you think we should accept an infinite causal chain as a candidate, which would be devastating to Aquinas' argument from causation ?