The origin of world we exist in has only three possible explanations. No fourth.
1-It had no beginning and always existed.
2-It created itself.
3-Another force brought it into existence.
The first one is a logical absurdity as it requires us to believe in an infinite series of causes and effects that have no origin. Like a series of dominoes knocking down one another with no beginning nor end.
The second one is also a logical absurdity in that it would require a thing to exist and not exist simultaneously at the same moment, which is impossible.
The third one is possible. There is nothing logically impossible with the idea of a force we don't know about that made this universe. And logically, this force must be uncreated, for if it was created, then it would be just another link in the infinite domino effect of causes.
If it is uncreated, then time is not applicable to it, as cause/effect and time are intertwined and inseparable. If there is no cause/effect nor time, then there is no space nor matter either, for space and matter are merely agents of cause and effect, which in turn is an agent of time.
Therefore, by intellect alone, it can be deduced that this world has a maker that is uncreated and exists independently of time, space and matter. What else do we know about this maker by intellect alone? Nothing.
Intellect alone is enough for a person to reject paganism and idolatry. But anything else about this maker can only be known through the phenomenon called prophecy, which can only be trusted by either direct meeting or documented reliable transmission, which we have in the form of Quran and authenticated hadith.
There were some people in the past that rejected idols by merely intellect and fitra, but never met a prophet and did not know anything else except that idols were false. Some refer to them as Sabians, which in Arabic means rejectors, for all they could do was reject falsehood.